This study evaluated the efficacy of 2 brief interventions for cannabis-dependent adults. A multisite randomized controlled trial compared cannabis use outcomes across 3 study conditions: (a) 2 sessions of motivational enhancement therapy (MET); (b) 9 sessions of multicomponent therapy that included MET, cognitive-behavioral therapy, and case management; and (c) a delayed treatment control (DTC) condition. Participants were 450 adult marijuana smokers with a Diagnostic and Statistical Manual of Mental Disorders (4th ed.; American Psychiatric Association, 1994) diagnosis of cannabis dependence. Assessments were conducted at baseline, and at 4, 9, and 15 months postrandomization. The 9-session treatment reduced marijuana smoking and associated consequences significantly more than the 2-session treatment, which also reduced marijuana use relative to the DTC condition. Most differences between treatments were maintained over the follow-up period. Discussion focuses on the relative efficacy of these brief treatments and the clinical significance of the observed changes in marijuana use.