Treating cocaine abuse is difficult because cocaine causes physical and behavioral changes in the body that reinforce the addicts' need for the drug. As a result, the rate of relapse of cocaine abuse is very high. A vaccine against cocaine would create cocaine-specific antibodies. The antibodies would work to immunize addicts against the effects of cocaine by reducing the drug's concentration in the brain. This study will use PET to measure the changes of cocaine distribution within the brain and body following anti-cocaine vaccination.

Participants in this study will be assigned to one of two groups for a total of 12 weeks. Group A participants will be recruited from a concurrent study, in which a cocaine vaccine will be administered. Group B participants will not receive the cocaine vaccine. Baseline assessments, including two PET scans, will be performed for both groups during an inpatient phase. The first PET scan will follow an injection of a cocaine tracer dose. The second PET scan will follow injection of a cocaine tracer dose combined with a low dose of cocaine. Both scans will assess the extent of infiltration of cocaine in the body. The cocaine vaccine will then be administered to Group A. Members of Group B will return to the study site weekly during the 11 weeks between scans to assess general health and well-being. Each visit will last 15 to 30 minutes. PET scans will be performed again at Week 12 for both groups. Follow-up visits will be held for both groups between 1 and 7 days following each scanning day. At this time, participants will receive a medical exam, a psychiatric assessment, blood tests, and an electrocardiogram.

Inclusion Criteria:

• Meets DSM-IV criteria for current cocaine dependence
• Primary route of cocaine intake is smoking

Exclusion Criteria:

• Current DSM-IV Axis I disorder other than cocaine abuse or dependence
• Currently meets DSM-IV criteria for dependence on substances other than cocaine or nicotine
• Currently taking psycotropic medications (e.g., antidepressants, antipsychotics)
• History of or current bipolar disorder or other psycotic disorder
• History of or current severe medical or neurological illness, including ongoing active infection
• Resting systolic blood pressure greater than 150 mm Hg and a diastolic blood pressure greater than 90 mm Hg
• Current abnormal thyroid indices
• Current heart abnormality
• Current pseudocholinesterase deficiency
• Currently seeking treatment for cocaine dependence
• History of psychosis as a resut of substance abuse
• History of exposure to radiation in the workplace
• History of a nuclear medicine procedure in the year prior to study entry (the following criteria will allow eligibility: participation in a protocol from the Division of Functional Brain Mapping with a known injected dose and dosimetry of the radiotracer; no lifetime exposure to radiation, aside from participation in research studies; a yearly cumulative exposure lower than the limit defined by the FDA for reserach study participants upon adding any previous exposure to the exposure from this study)

Additional Exclusion Criteria for Participants in Group A:

• History of autoimmune disease, immune deficiency, or hypersensitivity to vaccines
• Postive HIV test
• Recipient of a blood transfusion or recipient of blood products within 3 months prior to vaccination
• Has been vaccinated within 30 days of participation in the study (includes flu vaccine)
• Currently taking immunosuppressive drugs