M/F ages 21-45 with a history of smoked cocaine use at least twice a week for the past six months, including 0.5 g of cocaine in a 24hr period on at least one occasion. In good health as evidenced by physical exam and complete blood count, chest X-ray and electrolyte and liver function tests, with a normal resting 12-lead electrocardiograph (ECG) and blood pressure of less than 140/90 mmHg. Using an acceptable method of birth control. Having a urine toxicology screen positive for cocaine metabolites.