Study participants were drawn from 166 adolescents interviewed during an inpatient stay at one of two adolescent alcohol and other drug treatment programs in metropolitan San Diego, Calif. A total of 141 of the 166 adolescents interviewed while in treatment were current smokers (had smoked within the previous week), and thus they were eligible for inclusion in the analyses. Of the initial 141 smokers, 4-year follow-up data were available for 125. The final sample included 50 females (40 percent of the sample) and 75 males. The subjects came from varied socioeconomic backgrounds. During treatment each adolescent and resource person (parent) completed a 90-minute independent structured clinical interview during the second or third week of inpatient treatment for alcohol and drug abuse. Data were obtained on demographics and background information; pretreatment cigarette, alcohol, and drug use; and posttreatment cigarette, alcohol, and drug use. Analyses found that the age at initial cigarette use and extent of smoking at the time of treatment significantly predicted late adolescent/early adult smoking for male but not female participants. Those no longer smoking at the 4-year time-point reported less alcohol and drug involvement than those whose smoking persisted. The substantial persistence of cigarette smoking into early adulthood reinforces the need for smoking intervention with adolescent substance abusers. 2 tables and 24 references