This is a continuation application for a project examining the influence of other drug use on human cocaine use using a laboratory model. The prior project focused on the influence of non-prescription drug use (i.e., alcohol, caffeine, marijuana, and nicotine) and the proposed project will focus on the influence of prescription drug use (i.e., psychomotor stimulants, sedative hypnotics, and opioid analgesics). Understanding the influence of such other drug use on the probability of cocaine use is essential to the development of effective clinical strategies for managing polydrug abuse in cocaine treatment clinics, and could also prove useful to the development of effective pharmacotherapies for cocaine abuse. Laboratory models are important due to the rigorous experimental control they afford and their lower costs compared to clinical trials. In our laboratory model, volunteers participate in a series of experimental sessions in which they make exclusive choices between doses of intranasal cocaine and varying amounts of money. In studies completed to date (l) cocaine use varied as an orderly function of monetary value, demonstrating experimental control over drug use; (2) acute alcohol, but not caffeine, pretreatment increased preference for cocaine over the alternative monetary option, suggesting the model has pharmacological sensitivity and selectivity; and (3) these laboratory findings were concordant with evidence from clinic studies with cocaine-dependent patients, supporting the generalizability of these observations to treatment settings. Six studies are proposed for the next funding period. All examine the acute effects of prescription drugs that are commonly used and abused by cocaine abusers. The specific drugs proposed for study are damphetamine, methylphenidate, pentobarbital, triazolam, codeine, and buprenorphine. These studies wTh provide important new information on (l) how use of these drugs alters preference for cocaine versus alternative, non-drug reinforcers, (2) possible differences between drugs in how they affect cocaine use, and (3) the utility of laboratory models for addressing clinically important issues. Additionally, by examining non-prescription (prior application) and prescription (this application) drugs, this project will contribute a comprehensive experimental analysis of the influence of commonly used drugs on human cocaine use.