Of 365 undergraduates surveyed, 42% admitted to polydrug use. The rank order of drugs used was: alcohol, marijuana, tobacco, hallucinogens, barbiturates, amphetamines, cocaine, opiates, and inhalants. Forty-four percent used one drug combination, 25% used 2 to 3 combinations, 17% used 4 to 7 combinations, with 14% using 8 to 14 combinations. Nealry 85% used alcohol plus marijuana, with nearly one-third combining alcohol or marijuana with barbiturates, hallucinogens, or amphetamines. Alcohol appeared to be first drug used; however, it was not abandoned when marijuana use began-both drugs simply used concurrently, and new drugs were incorporated into the existing patterns of drug use. Interpretations of polydrug use are limited by difficulties in assessing drug use, as well as inconsistencies in the chemical composition of illicit drugs.