The L Legislature of the Congress of the Union met from 1976 to 1979. This 50th session of Congress consisted of senators and deputies who were members of their respective chambers. They began their duties on September 1, 1976, and ended on August 31, 1979.

The senators and deputies were elected to office in the 1976 Mexican general election. The senators were elected for a period of six years (so they maintained their seat in the next legislature), and the deputies were elected for a period of three years.

The composition of the 50th Congress was as follows:

Two members were elected to the Senate from each state and the Federal District, giving a total of 64 senators. For the first time in history a senator was elected who did not belong to the Institutional Revolutionary Party (PRI).^[1] Jorge Cruickshank García had been nominated by the PPS;^[1] the PRI did not lose this seat, however, because it formed an electoral alliance with the winning party. Thus this senator posed no opposition to the PRI or the government during his term.

Party		Senators
	Institutional Revolutionary Party	63
	Popular Socialist Party	1

The 64 Senators forming the L Legislature were the following:

State	Senator	Party	State	Senator	Party
Aguascalientes	Rodolfo Landeros Gallegos		Nayarit	Leobardo Ramos Martínez
Aguascalientes	Héctor Hugo Olivares Ventura[1]		Nayarit	Daniel Espinoza Galindo
Baja California	Rafael García Vázquez Replaced Roberto de la Madrid Romandía		Nuevo León	Napoleón Gómez Sada
Baja California	Oscar Baylón Chacón		Nuevo León	Adrián Yáñez Martínez
Baja California Sur	Alberto Alvarado Arámburo		Oaxaca	Rodolfo Alaves Flores
Baja California Sur	Víctor Manuel Liceaga Ruibal Replaced Marcelo Rubio Ruiz[a]		Oaxaca	Jorge Cruickshank García[1]
Campeche	Rosa María Martínez Denegri Replaced Carlos Sansores Pérez		Puebla	Horacio Labastida Muñoz
Campeche	Joaquín Repetto Ocampo Replaced Fernando Rafful Miguel		Puebla	Blas Chumacero
Chiapas	Roberto Corzo Gay		Querétaro	Rafael Camacho Guzmán
Chiapas	Horacio Castellanos Coutiño		Querétaro	Telésforo Trejo Uribe
Chihuahua	Óscar Ornelas		Quintana Roo	Vicente Coral Martínez
Chihuahua	Mario Carballo Pazos		Quintana Roo	José Blanco Peyrefitte
Coahuila	Eliseo Mendoza Berrueto		San Luis Potosí	Rafael Tristán López
Coahuila	Gustavo Guerra Castaños		San Luis Potosí	Francisco Padrón Puyou
Colima	Griselda Álvarez		Sinaloa	Hilda Anderson Nevárez
Colima	Antonio Salazar y Salazar		Sinaloa	Gilberto Ruiz Almada
Durango	Ignacio Castillo Mena		Sonora	Juan José Gastelum García
Durango	Tomás Rangel Perales		Sonora	Adolfo de la Huerta Oriol
Guanajuato	Euquerio Guerrero López		Tabasco	Antonio Ocampo Ramírez Replaced Carlos Pellicer
Guanajuato	Jesús Cabrera Muñoz Ledo		Tabasco	Nicolás Reynés Berazaluce Replaced David Gustavo Gutiérrez
Guerrero	Jorge Soberón Acevedo		Tamaulipas	Morelos Jaime Canseco González
Guerrero	Alejandro Cervantes Delgado		Tamaulipas	Martha Chávez Padrón
Hidalgo	Humberto Lugo Gil		Tlaxcala	Jesús Hernández Rojas
Hidalgo	Vacant By leave of Guillermo Rossell de la Lama and Jorge Rojo Lugo		Tlaxcala	Rafael Minor Franco
Jalisco	José María Martínez Rodríguez		Veracruz	Silverio Ricardo Alvarado
Jalisco	Arnulfo Villaseñor Saavedra		Veracruz	Sergio Martínez Mendoza
State of Mexico	Leonardo Rodríguez Alcaine		Yucatán	Víctor Cervera Pacheco
State of Mexico	Gustavo Baz		Yucatán	Graciliano Alpuche Pinzón
Michoacán	José Luis Escobar Herrera Replaced Cuauhtémoc Cárdenas Solórzano		Zacatecas	Jorge Gabriel García Rojas
Michoacán	Guillermo Morfín García		Zacatecas	José Guadalupe Cervantes Corona
Morelos	Angel Ventura Valle		Federal District of Mexico	Luis del Toro Calero Replaced Hugo Cervantes del Río
Morelos	Javier Rondero Zubieta		Federal District of Mexico	Joaquín Gamboa Pascoe

For the L Legislature, the Chamber of Deputies was composed of a total of 238 deputies, of whom 196 were elected by majority vote in each constituency and 41 more were deputies by party. These were allocated in proportion to the votes that the non-winning parties obtained in the districts.

The composition of the Chamber of Deputies during the 50th session of Congress was as follows:

	Party	Deputies
	Institutional Revolutionary Party	196[2]
	National Action Party	20[2]
	Popular Socialist Party	12[2]
	Partido Auténtico de la Revolución Mexicana	9[2]

State	District	Deputy	Party	State	District	Deputy	Party
Aguascalientes	1	Jesús Martínez Gortari		México	8	Armando Labra Manjarrez
Aguascalientes	2	Camilo López Gómez		México	9	Juan Ortíz Montoya
Baja California	1	Ricardo Eguía Valderrama		México	10	José Luis García García
Baja California	2	Alfonso Ballesteros Pelayo		México	11	Guillermo Choussal Valladares
Baja California	3	Alfonso Garzón Santibáñez		México	12	Cecilio Salas Gálvez
Baja California Sur	1	Víctor Manuel Peralta Osuna		México	13	Pedro Ávila Hernández
Baja California Sur	2	Agapito Duarte Hernández		México	14	Armando Hurtado Navarro
Campeche	1	Abelardo Carrillo Zavala		México	15	Héctor Ximénez González
Campeche	2	Jorge Muñoz Icthé		Michoacán	1	Nicanor Gómez Reyes
Chiapas	1	Jaime Sabines		Michoacán	2	Antonio Jaimes Aguilar
Chiapas	2	Fernando Correa Suárez		Michoacán	3	Raúl Lemus García
Chiapas	3	Homero Tovilla Cristiani		Michoacán	4	Roberto Garibay Ochoa
Chiapas	4	Manuel Villafuerte Mijangos		Michoacán	5	Jaime Bravo Ramírez
Chiapas	5	Gonzalo Esponda Zebadúa		Michoacán	6	Eduardo Estrada Pérez
Chiapas	6	Leonardo León Cerpa		Michoacán	7	Juan Rodríguez González
Chihuahua	1	Alberto Ramírez Gutiérrez		Michoacán	8	Héctor Terán Torres
Chihuahua	2	Oswaldo Rodríguez González		Michoacán	9	Roberto Ruiz del Río
Chihuahua	3	José Reyes Estrada Aguirre		Morelos	1	Antonio Riva Palacio López
Chihuahua	4	Juan Ernesto Madera Prieto		Morelos	2	Filomeno López Rea
Chihuahua	5	Artemio Iglesias		Nayarit	1	Ignacio Langarica Quintana
Chihuahua	6	José Refugio Mar de la Rosa		Nayarit	2	María Hilaria Domínguez Arvizu
Coahuila	1	José de las Fuentes Rodríguez		Nuevo León	1	Carlota Vargas Garza
Coahuila	2	Carlos Ortiz Tejeda		Nuevo León	2	Heriberto Santos Lozano
Coahuila	3	Fernando Cabrera Rodríguez		Nuevo León	3	Raúl Caballero Escamilla
Coahuila	4	Julián Muñoz Uresti		Nuevo León	4	Eleazar Ruiz Cerda
Colima	1	Ramón Serrano García		Nuevo León	5	Arturo Luna Lugo
Colima	2	Fernando Moreno Peña		Nuevo León	6	Jesús Puente Leyva
Federal District	1	Eduardo Andrade Sánchez[3]		Nuevo León	7	Roberto Olivares Vera
Federal District	2	José Salvador Lima Zuno		Oaxaca	1	Lucía Betanzos de Bay
Federal District	3	Carlos Riva Palacio Velazco		Oaxaca	2	Gustavo Santaella Cortés
Federal District	4	Enrique Ramírez y Ramírez		Oaxaca	3	Ericel Gómez Nucamendi
Federal District	5	Miguel Molina Herrera		Oaxaca	4	Ernesto Aguilar Flores
Federal District	6	Alfonso Rodríguez Rivera		Oaxaca	5	Luis Candelario Jiménez Sosa
Federal District	7	María Elena Márques de Torruco[4]		Oaxaca	6	Heladio Ramírez López
Federal District	8	Julio César Mena Brito		Oaxaca	7	Zoraida Bernal de Badillo
Federal District	9	Venustiano Reyes López		Oaxaca	8	Julio Esponda Solana
Federal District	10	Gloria Carrillo Salinas		Oaxaca	9	Raúl Bolaños Cacho Guzmán
Federal District	11	Jaime Aguilar Álvarez		Puebla	1	Nicolás Pérez Pavón
Federal District	12	Miguel López Riveroll		Puebla	2	Jorge Domínguez Ramírez
Federal District	13	Rodolfo González Guevara		Puebla	3	Antonio Montes García
Federal District	14	Jorge Mendicutti Negrete		Puebla	4	Antonio Hernández Jiménez
Federal District	15	Juan José Osorio Palacios		Puebla	5	Sacramento Jofre Vázquez
Federal District	16	Alfonso Argudín Laria		Puebla	6	Antonio Tenorio Adame
Federal District	17	Héctor Hernández Casanova		Puebla	7	Guadalupe López Bretón
Federal District	18	Hugo Díaz Velázquez		Puebla	8	Jesús Sarabia y Ordóñez
Federal District	19	Abraham Martínez Rivero		Puebla	9	Jorge Murad Macluf Replaced Manuel Rivera Anaya
Federal District	20	Jesús González Balandrano		Puebla	10	Adolfo Rodríguez Juárez
Federal District	21	Martha Andrade de Del Rosal		Querétaro	1	Eduardo Ugalde Vargas
Federal District	22	Ifigenia Martínez[5]		Querétaro	2	Vicente Montes Velázquez
Federal District	23	Enrique Soto Izquierdo		Quintana Roo	1	Carlos Gómez Barrera
Federal District	24	Enrique Álvarez del Castillo		Quintana Roo	2	Emilio Oxte Tah
Federal District	25	Celia Torres de Sánchez		San Luis Potosí	1	Roberto Leyva Torres
Federal District	26	Humberto Serrano Pérez[6]		San Luis Potosí	2	Guadalupe Vega Macías
Federal District	27	Hugo Roberto Castro Aranda		San Luis Potosí	3	Víctor Maldonado Moreleón
Durango	1	Ángel Sergio Guerrero Mier		San Luis Potosí	4	Héctor González Lárraga
Durango	2	Maximiliano Silerio Esparza		San Luis Potosí	5	Eusebio López Sáinz
Durango	3	Salvador Reyes Nevárez		Sinaloa	1	Tolentino Rodríguez Félix
Durango	4	José Ramírez Gamero		Sinaloa	2	Felipe Armenta Gallardo
Guanajuato	1	Esteban Mario Garaiz		Sinaloa	3	Rafael Oceguera Ramos
Guanajuato	2	Enrique Gómez Guerra		Sinaloa	4	Antonio Toledo Corro
Guanajuato	3	Juan Varela Mayorga		Sinaloa	5	Patricio Robles Robles
Guanajuato	4	Miguel Montes García		Sonora	1	Ricardo Castillo Peralta
Guanajuato	5	Aurelio García Sierra		Sonora	2	César Augusto Tapia Quijada
Guanajuato	6	Alfredo Carrillo Juárez		Sonora	3	José Luis Vargas González
Guanajuato	7	Enrique León Hernández		Sonora	4	Bernabé Arana León
Guanajuato	8	Graciela Meave Torrescano		Tabasco	1	Luis Priego Ortiz
Guanajuato	9	Donaciano Luna Hernández		Tabasco	2	Roberto Madrazo Pintado
Guerrero	1	Isaías Gómez Salgado		Tabasco	3	Francisco Rabelo Cupido
Guerrero	2	Isaías Duarte Martínez		Tamaulipas	1	Abdón Rodríguez Sánchez
Guerrero	3	Miguel Bello Pineda		Tamaulipas	2	Oscar Mario Santos Gómez
Guerrero	4	Hortensia Santoyo de Martínez		Tamaulipas	3	Agapito González Cavazos
Guerrero	5	Reveriano García Castrejón		Tamaulipas	4	Aurora Cruz de Mora
Guerrero	6	Salustio Salgado Guzmán		Tamaulipas	5	Fernando San Pedro Salem
Hidalgo	1	Ladislao Castillo Feregrino		Tamaulipas	6	Julio Martínez Rodríguez
Hidalgo	2	Luis José Dorantes Segovia		Tlaxcala	1	Nazario Romero Díaz
Hidalgo	3	Efraín Mera Arias		Tlaxcala	2	Antonio Vega García
Hidalgo	4	José Antonio Zorrilla Pérez		Veracruz	1	Guilebaldo Flores Fuentes
Hidalgo	5	Vicente Trejo Callejas		Veracruz	2	Pericles Namorado Urrutia
Jalisco	1	Guillermo Cosío Vidaurri		Veracruz	3	Emilio Salgado Zubiaga
Jalisco	2	Reynaldo Dueñas Villaseñor		Veracruz	4	Manuel Gutiérrez Zamora Zamudio
Jalisco	3	Félix Flores Gómez		Veracruz	5	Seth Cardeña Luna
Jalisco	4	Porfirio Cortés Silva		Veracruz	6	Carlos Manuel Vargas Sánchez
Jalisco	5	José Mendoza Padilla		Veracruz	7	Daniel Nogueira Huerta
Jalisco	6	Rigoberto González Quezada		Veracruz	8	Celeste Castillo Moreno
Jalisco	7	Ma. Refugio Castillón Coronado		Veracruz	9	Mario Martínez Dector
Jalisco	8	Ricardo Chávez Pérez		Veracruz	10	Pastor Munguía González
Jalisco	9	María Guadalupe Urzúa Flores		Veracruz	11	Miguel Portela Cruz
Jalisco	10	Francisco Javier Santillán Oceguera		Veracruz	12	Mario Hernández Posadas
Jalisco	11	Héctor Castañeda Jiménez		Veracruz	13	Francisco Cinta Guzmán
Jalisco	12	Rafael González Pimienta		Veracruz	14	Juan Meléndez Pacheco
Jalisco	13	Jesús Alberto Mora López		Veracruz	15	Eduardo Thomae Domínguez
México	1	Gildardo Herrera		Yucatán	1	Mirna Hoyos Schlamme
México	2	Josefina Esquivel de Quintana		Yucatán	2	Rubén Calderón Cecilio
México	3	José Delgado Valle		Yucatán	3	Víctor Manzanilla Schaffer
México	4	Arturo Martínez Legorreta		Zacatecas	1	Gustavo Salinas Íñiguez
México	5	José Martínez Martínez		Zacatecas	2	Crescencio Herrera Herrera
México	6	Rosendo Franco Escamilla		Zacatecas	3	José Leal Longoria
México	7	Julio Zamora Bátiz		Zacatecas	4	Julián Macías Pérez

Deputy	Party	Deputy	Party	Deputy	Party
Fausto Alarcón Escalona		José Ortega Mendoza		Eugenio Soto Sánchez
Gonzalo Altamirano Dimas		Francisco Pedraza Villarreal		Rafael Campos López
María Elena Álvarez Bernal		Francisco José Peniche Bolio		Víctor Manuel Carrasco
Miguel Campos Martínez		Adrián Peña Soto		Felipe Cerecedo López
Guillermo Carlos de Carcer		Jacinto Silva Flores		Alberto Contreras Valencia
Jorge Garabito Martínez		Juan Torres Ciprés		Francisco Hernández Juárez
Ramón Garcilita Partida		Saúl Castorena Monterrubio		Marcela Lombardo Otero
Miguel Hernández Labastida		Fortino Garza Cárdenas		Jesús Luján Gutiérrez
Guillermo Islas Olguín		Pedro González Azcuaga		Francisco Ortiz Mendoza
Sergio Lujambio Rafols		Raúl Guillén Pérez Vargas		Román Ramírez Contreras
Rosalba Magallón Camacho		Manuel Hernández Alvarado		Héctor Ramírez Cuéllar
José Luis Martínez Galicia		Edilio Hinojosa López		Idelfonso Reyes Soto
Tomás Nava de la Rosa		Apolinar Ramírez Meneses		Ezequiel Rodríguez Otal
Teodoro Ortega García		Arcelia Sánchez

• 1976–1977: Augusto Gómez Villanueva
• 1977–1979: Rodolfo González Guevara
• 1979: Antonio Riva Palacio López

It was the 50th Congress that, in 1977, adopted the first political reforms to occur in Mexico. This reform, negotiated by Secretary of the Interior Jesús Reyes Heroles, included legal recognition of political organizations from the left, traditionally marginalized and pushed into armed struggle, especially after the events of 1968 and which degenerated into a "Dirty War" during the 1970s.^[7]

Legal reform, known formally as the Ley de Organizaciones Políticas y Procedimientos Electorales (LOPPE) (Law of Political Organizations and Electoral Procedures), defined and made possible procedures for the registration of new political parties (in 1977 legally there were only the PRI, the National Action Party) (PAN), the Popular Socialist Party (PPS) and the Authentic Party of the Mexican Revolution (PARM)).^[2] This allowed for the registration, for the first time in 40 years of the Mexican Communist Party, which was followed by the National Assembly of the Socialist Left, the Mexican Democratic Party and the Social Democratic Party.

In addition, the (LOPPE) increased the size of the Chamber of Deputies, increasing the number of electoral districts from 196 to 300, and establishing deputies by proportional representation, replacing the previous deputies by party.^[7] There would be 100 such positions, resulting in the Chamber of Deputies comprising 400 deputies.^[2][8]

• Congress of the Union
• Mexico Chamber of Deputies
• Senate of the Republic (Mexico)

• Official page of the Chamber of Deputies
• Official page of the senate