Participants in this double-blind, placebo-controlled trial will be randomly assigned to receive either NAC or placebo. All participants will undergo an initial evaluation, which will include a physical examination, an electrocardiogram, blood samples, urine tests, and cue reactivity measures. Participants in the NAC group will receive either 600 mg or 1200 mg of NAC, two times each day for 8 weeks. In addition, all participants will receive cognitive behavioral therapy throughout the study on a weekly basis. Cocaine use will be confirmed by a urine drug screen test, three times each week. Participants will be assessed on a number of biomedical and psychosocial variables known to influence cocaine treatment outcomes. After Week 2, participants will repeat the cue reactivity procedures, which will include measuring a participant's craving response when exposed to conditioned reminders of prior cocaine use.