Inclusion Criteria:

• Male or female individuals, ages 18-50, meeting current DSM-IV criteria for cocaine and/or alcohol dependence.
• COCAINE SAMPLE: meet current DSM-IV criteria for cocaine dependence; documented positive urine toxicology screen for cocaine at intake
• ALCOHOLIC SAMPLE: meet current DSM-IV criteria for alcohol dependence
• Subject has voluntarily given informed consent and signed the informed consent document.
• Able to read English and complete study evaluations.

Exclusion Criteria:

• Meet current criteria for dependence on another psychoactive substance, excluding nicotine and caffeine;
• Any current use of opiates or past history of opiate abuse/dependence;
• Current use of any psychoactive drugs, including anxiolytics, antidepressants, naltrexone or antabuse;
• Any psychotic disorder or current Axis I psychiatric symptoms requiring specific attention, including need for psychiatric medications for current major depression and anxiety disorders
• Significant underlying medical conditions such as cerebral, renal, thyroid or cardiac pathology which in the opinion of study physician would preclude patient from fully cooperating or be of potential harm during the course of the study;
• Abstinent from cocaine for more than two weeks prior to admission.
• Hypotensive individuals with sitting blood pressure below 90/50 mmHG.