The 598 participants were 9th, 10th, and 11th grade students in 2 urban public high schools in Philadelphia during academic year 1980-81. The students reported on their use of alcohol, marijuana, inhalants, and several other types of drugs and on other problem behavior. The data were analyzed by means of multiple regression techniques. The sample was divided into three groups: (1) those with no reported history of illicit drug use; (2) those who used marijuana, alcohol, or both at least weekly during the previous 3 months; and (3) those who used drugs less often. Results revealed a highly significant relationship between drug use and school failure. The majority of the regular drug users dropped out of high school before graduation. The dropouts represented 26 percent of the non-drug users, 30 percent of the casual drug users, and 51 percent of the regular drug users. Dropouts were more likely than graduates to be male, have separated parents, have a large number of household members, and have mothers with less education. Findings indicated that significant juvenile drug use interferes with academic and career progress. Tables and 6 references