Inclusion Criteria:

1. Subjects must be able to provide informed consent and function at an intellectual level sufficient to allow accurate completion of all assessment instruments.
2. Subjects must meet DSM-IV criteria for current cocaine dependence. Subjects may meet criteria for abuse, but not dependence on any other substance within the past 60 days with the exception of nicotine. Because of the high comorbidity of cocaine and nicotine dependence, excluding nicotine dependence would seriously compromise the feasibility of recruitment. Nicotine use immediately prior to the testing session will be controlled. Alcohol has also been known to affect HPA function (Adinoff et al., 1991), however to enhance recruitment efforts individuals with alcohol dependence or abuse will be included in the study if they do not require medically supervised detoxification.
3. Use of one of the following methods of birth control by female subjects: barrier methods (diaphragm or condoms with spermicide or both), surgical sterilization, use of an intra-uterine contraceptive device, or complete abstinence from sexual intercourse.
4. Subjects must live within a 50-mile radius of our research program and have reliable transportation.
5. Subjects must consent to remain abstinent from all drugs of abuse (except nicotine or alcohol) for 24 hours immediately prior to the GCRC admission.
6. Subjects must consent to random assignment to the DCS vs. placebo conditions.

Exclusion Criteria:

1. Women who are pregnant, nursing or of childbearing potential and not practicing an effective means of birth control.
2. Subjects with evidence of or a history of significant hematological, endocrine, cardiovascular, pulmonary, renal, gastrointestinal, or neurological disease including diabetes, as these conditions may affect heart rate or skin conductance measurement.
3. Individuals with creatinine clearance of 1.2 or greater as DCS is renally excreted.
4. Subjects with a history of or current psychotic disorder, current major depressive disorder, bipolar affective disorder or a severe anxiety disorder as these may impact cue reactivity.
5. Subjects who are unwilling or unable to maintain abstinent from alcohol and other drugs of abuse (except nicotine) for 24 hours days prior to the cue procedure.
6. Subjects meeting DSM-IV criteria for substance dependence (other than nicotine or cocaine as appropriate) within the past 60 days.
7. Subjects currently taking B-blockers, anti-arrythmic agents, psychostimulants or any other agents known to interfere with heart rate and skin conductance monitoring.
8. Known or suspected hypersensitivity to DCS.
9. Individuals taking medications that could adversely interact with study medications, including, but not limited to ethionamide, isoniazid, or amino acid supplements.
10. Subjects with a history of epilepsy or seizure disorder.
11. Subjects with significant liver impairment as DCS may increase serum transaminases.