The first typology is based on reported use of seven drugs (alcohol, marijuana, hallucinogens, amphetamines, barbiturates, cocaine, and heroin) by the youth panel in 1976. The second is an integrated typology based on reported use of an expanded set of 12 drugs (including tobacco, angel dust, and inhalants) by the youth panel in 1977 and 1978. A major conclusion from this analysis is that adolescent drug consumption consists primarily of multiple drug use rather than single drug use. Of the youth who consume drugs, the vast majority use more than one drug during a given time period. A second general conclusion is that the empirical patterns of drugs use are complex. A pattern may involve the regular use of two drugs and an experimental or intermittent use of two or three other drugs. The most frequent developmental pattern for multiple drug use is the occasional use of alcohol; regular use of beer and hard liquor; regular use of alcohol and tobacco; regular use of alcohol, tobacco, and marijuana; and multiple illicit drug use. There was a clear association between the drug-use patterns ordered by the frequency and number of drugs used and various types of problem behavior, delinquency, and measures of bonding to conventional groups' norms and activities. Data address the demographic characteristics of drug use, including types and pattern of onset, termination, increasing use, and decreasing use. 3 figures, 25 tables, and 20 references