[1] It elects one deputy to the lower house of Congress for each three-year legislative period by means of the first-past-the-post system.

Votes cast in the district also count towards the calculation of proportional representation ("plurinominal") deputies elected from the third region.

[a] The district's head town (cabecera distrital), where results from individual polling stations are gathered together and tallied, is the city of Ciudad Ixtepec in the Istmo de Tehuantepec region.

Under the 2017 to 2022 scheme, the 7th district had its head town at Ciudad Ixtepec and it covered 24 municipalities.

[11][10] The districting scheme in force from 1978 to 1996 was the result of the 1977 electoral reforms, which increased the number of single-member seats in the Chamber of Deputies from 196 to 300.