The 19 juvenile participants reported using marijuana during the previous 30 days or had a marijuana-positive urine test result, and they lived with a parent/guardian who agreed to participate. Seventeen mothers and 14 fathers participated in treatment. An initial evaluation assessed juvenile substance use and related risk factors such as adolescent, family, and parent characteristics. Treatment involved one 90-minute weekly therapy session for 14 consecutive weeks and twice-weekly drug testing. Each session included a brief check-in with the adolescent and parent(s), a 40-minute individual session with the juvenile, a 40-minute session with the parent(s) alone, and a brief wrap-up with everyone together. The juveniles provided urine specimens at each session and at a second appointment between sessions. The abstinence-based incentive program is designed so that substance use and its absence are readily detected, abstinence is reinforced, substance use results in a loss of reinforcement, and positive reinforcement gleaned from drug abstinence is used to increase nondrug reinforcement. Juveniles and parents attended an average of 10.3 and 10.6 of 14 sessions, respectively. Substance use, externalizing behaviors, and negative parenting behaviors decreased by treatment end. Urine testing indicated that abstinence increased from 37 percent at intake to 74 percent at treatment end and that 53 percent of the juveniles were abstinent 30 days after treatment. Preliminary data provide support for the feasibility and acceptability of a family-based contingency management model in the treatment of adolescent substance use and conduct problems; however, controlled evaluation studies with larger samples are needed. 3 tables, 1 figure, and 38 references