A definable and significant withdrawal syndrome occurs upon cessation of chronic, heavy marijuana use. This syndrome includes alterations in mood, sleep disturbances, and cognitive performance. Many of nicotine's withdrawal symptoms are similar to those observed with marijuana withdrawal. Bupropion has been shown to be effective in treating nicotine addiction.The purpose of this study is to determine if bupropion is effective in treating marijuana dependent individuals. Specifically, this study will determine if bupropion alleviates withdrawal symptoms associated with marijuana abuse.