Participants in this study will include 20 non-treatment seeking cocaine dependent individuals and 12 healthy, non-dependent controls. Participants will be recruited via word-of-mouth and advertisements. Cocaine dependent participants will undergo two 3-day hospital stays. Healthy controls will be followed throughout the study on an outpatient basis. All participants will be randomly assigned to receive either 600 mg of NAC or placebo. Medication or placebo will be administered twice each day. Participants will be evaluated for side effects throughout the study. After administration of the final dose of medication or placebo, participants will undergo cue reactivity testing. This will include a standardized protocol of slides demonstrating cocaine acquisition, use of cocaine, and cocaine-related paraphernalia. Before, during, and after cue reactivity procedures, standardized behavioral and cognitive scales will be used to assess cocaine craving, cocaine seeking, and subjective effects of the cocaine "high." The following week participants will be crossed over so that they will receive the other treatment. All study procedures will be performed a second time. Participants will be contacted during Week 3 in order to determine if any residual side effects or adverse events occurred from the medication and treatment.