1. The present study evaluated neuropsychological differences among 4 groups of men and women, aged 15 to 61 years. The groups were defined on the basis of urine toxicology screens indicating recent cocaine (n = 12), cannabis (n = 14), or multiple drug (n = 7) use, or no such use (n = 21). 2. The Wechsler Adult Intelligence Scale-Revised (WAIS-R), the Trail Making Tests, and the Porteus Maze Test were administered to all subjects. 3. Analyses revealed no significant differences between the groups in age, gender composition, or in the proportion of group members with personal histories of alcohol/drug abuse or dependence, or Anti-Social Personality Disorder. 4. The cocaine positive group exhibited statistically significant impairments in Verbal IQ, as well as on Information, Vocabulary, Comprehension, Picture Completion, and Trails B subtests. The other experimental groups did not differ from the urine negative group.