The sample consisted of 460 males and 67 females and represented the diverse ethnic population of Santa Clara County. The analyses focused on gender and ethnic differences in blood alcohol level (BAL) and place of last drink. Information was also obtained on educational level, occupation, and income. The data showed that the typical DUI offender was a well-educated, middle-class male. Overall, women had higher blood alcohol levels than did the men. Ethnic group differences in BAL were not statistically significant. Gender and ethnic group differences were found in place of last drink. Nearly 50 percent of the non- Hispanic white DUI offenders reported they had consumed their last drink at a licensed liquor outlet. Hispanics and members of other ethnic groups typically took their last drink at their own house or a friend's house. Findings indicate that the social ecology of drinking for men and women and for members of various ethnic groups must be analyzed if more effective prevention and intervention strategies are to be implemented in Santa Clara County. 3 tables and 9 references