The purpose of the present study was to determine the prevalence of the concurrent and simultaneous use of alcohol and cocaine in the general population and to examine differences in these rates between important sociodemographic subgroups. The results indicated that a sizable proportion of Americans were engaged in both substance use patterns. The population estimate for simultaneous use of both substances (i.e., simultaneously or on the same occasion) was approximately 4 million for the month preceding the interview, rising to approximately 9 million when the past year timeframe was considered. Corresponding figures for the concurrent use of alcohol and cocaine (i.e., use of both substances during the same time period) were approximately 5 million during the past month and 12 million during the past year. The extent of each substance use practice varied as a function of sociodemographic factors. Implications of these findings are discussed in terms of the need for age-sex-ethnic-specific prevention strategies. The need for future analytic epidemiologic research to determine the precise relationship between dose, frequency and duration of concurrent and simultaneous use and each adverse consequence is emphasized. The need for longitudinal research in the general population is also highlighted.