During the 1980s the social distribution of adult cocaine use in the US changed, according to qualitative analyses, and its use became more prevalent in the lower as compared to the upper social strata. In this paper, we use national data to investigate the association of education and adult cocaine use to test whether this trend represents either a 'historical period' process that occurred concurrently across adults of all age groups or a cohort process that started with younger cohorts and only extended to older age groups as these younger cohorts aged. We also estimate the extent to which the emergence of crack cocaine use accounts for trends in the socioeconomic distribution of cocaine use over historical time. To address these questions we analyze data from each survey of the National Household Survey on Drug Abuse from 1979 to 1998 inclusive. The results point to a 'historical period' process that is explained in large part – but not entirely – by the emergence of crack cocaine. Important differences are apparent across racial and ethnic groups, as well as age groups. Cocaine use joins a growing list of potentially addictive drugs that have become more prevalent in the lower as compared to the upper social strata over historical time.