The drug abuse basic research center in the Department of Pharmacology of The University of Michigan is composed of established investigators who have independent, but interrelated, interests in problems related to drug abuse. Studies in the monkey colony are concerned with the development of physical dependence to new analgesic agents, to morphine antagonists and to compounds which have mixed agonist-antagonist properties. Self-administration studies in rhesus monkeys are used do evaluate the reinforcing properties of drug- taking behavior, to study the choices which the animals make between pairs of drugs or between a drug and another reinforcing modality. Biochemical studies are concerned with the influence of drugs of abuse upon such neurohumoral transmitters as serotonin, dopamine and norepinephrine. Drug transport into cells and drug localization in tissues is studied.