Males/Females between the ages of 20-40. History of smoked cocaine use on the avg. of at least 2 times/week over a 6 month period. Have currently used at least 1 g of cocaine within a 4-6 hr period. Current history of good health, normal serum albumin levels and normal QTc intervals. Nonreactive for HIV. No participation in any of our studies for the past 6 months. For females: not pregnant as determined by pregnancy screening nor breat feeding, and using acceptable birth control methods (e.g. birth control pills, diaphragm, condoms plus foam).