The papers cover social and medical effects of cocaine addiction and advances in the neurosciences over the past decade that emphasize the role of biological factors in the development of dependence, tolerance, and drug craving. Other papers examine cocaine addiction using positron emission tomography; describe how cocaine's affinity for the dopamine neuron is enhanced through its extremely rapid uptake in clearance from the brain; and explore effects of chronic cocaine administration on neurons concerned with dopamine, serotonin, and norepinephrine and on the endogenous opioid system. Finally, papers explain the coexistence of cocaine and heroin addiction, the decreasing incidence of cocaine use in former heroin addicts remaining in methadone treatment, the ability of opioids to decrease cocaine self- administration in animal models, cocaine trends in New York City, effects of contextual and psychological variables on daily cocaine use patterns, and crack cocaine dependence. References, tables, and figures