 Marijuana is the most commonly used illicit drug, yet few clinical trials have evaluated pharmacotherapy treatments for marijuana dependence. This study will evaluate the efficacy of buspirone for reducing marijuana use in marijuana-dependent adults. A contingency management CM intervention and motivational enhancement therapy MET will be incorporated to encourage study engagement and retention. It is hypothesized that buspirone combined with MET and CM will reduce the percent of marijuana-positive urine drug screen results in marijuana-dependent individuals as compared to a placebo treatment combined with MET and CM. 