Research will be conducted with human volunteers to examine the self-administration, reinforcing effects and behavioral pharmacology of abused drugs. The primary set of experiments will explore the self-administration and reinforcing of drugs within a residential research laboratory with volunteers with histories of drug abuse. These studies will evaluate various clinically used anorectic-stimulant drugs (e.g., amphetamine, diethylpropion, chlorphentermine, fenfluramine) and sedative drugs (e.g., diazepam, oxazepam and pentobarbital). A second set of studies will provide additional information about these drugs by examining their effects in normal outpatient volunteers. The particular emphasis of this set of studies will be on the interactive relationship between anorectic-stimulant drugs and human social behavior. A final set of studies will further extend the research on anorectic-stimulant drugs by systematically comparing the self-administration of these compounds in the therapeutic context of a treatment program for overweight. Overall, the results of these studies will contribute to improved understanding of and treatment procedures for nonopioid drug abuse.