This article assesses changes in absolute and relative opportunities of access to the upper strata of the urban social and occupational structure in Mexico, drawing on data from the largest retrospective social mobility survey carried out in the country, which covers all the largest cities and some medium-sized ones. It analyses intergenerational mobility in three periods: before 1982, from 1982 to 1988, and from 1988 to 1994. The results show a striking decline in opportunities of access to the stratum of professionals, managers and executives and large employers. This decline has not been linear but has affected first and foremost those from the lowest strata, then those from privileged strata, while leaving the intermediate strata of the sociooccupational structure virtually unaffected. The article also analyses the evolution of absolute and relative opportunities by gender. /