Conceptually, the pharmacodynamic and clinical actions of quetiapine suggest that it may be useful for cannabis dependence. By antagonizing dopamine, quetiapine may interfere with the reinforcing effects of cannabis, while serotonin type 2A, histamine type 1, and adrenergic receptor antagonism may reduce cannabis withdrawal symptoms, primarily by sedating and anxiolytic effects. The proposed research project is an open-label pilot study to evaluate the tolerability and ideal target dosing range for quetiapine treatment of cannabis dependence over an eight-week period. The purpose of this pilot study is to obtain preliminary data regarding the potential efficacy, tolerability and safety of quetiapine treatment of cannabis dependence before conducting a larger double-blind trial.