This five-year prospective study combines drug epidemiological and treatment evaluation information to assess treatment system utilization and effectiveness among drug-dependent users in Los Angeles County. Drug users will be assessed from non-treatment catchment sources where drug use prevalence among service clients is high and for whom treatment efforts are especially needed. Starting in the seventh month of the first study year, year-round surveys will be conducted to examine the drug use prevalence rates in selected emergency rooms, sexually transmitted disease clinics, and jails. Cumulatively, about 1,800 drug-dependent users, identified by self-report or other methods, will be interviewed on-site to obtain information about their past and current drug use patterns, treatment history, and knowledge and attitudes about drug use and treatment. This information will be updated in subsequent, prospectively designed follow-up interviews with subsets of the samples during the second through the fourth years of the project. Referral information about drug treatment and HIV-related services will be distributed at each contact and compliance will be subsequently assessed. In later project years, the feasibility of developing more effective alternate referral and outreach strategies will be examined. Expansion of sample sources to include AIDS education outreach programs and shelters or street outreach programs for the homeless will also be considered. A computerized system will be developed to establish the database and to provide timely data analysis. Extensive statistical analyses and modeling applications will be performed, particularly in the fifth study year. Rates of treatment entry/retention as well as factors facilitating treatment utilization and improving treatment outcomes will be analyzed. Comparisons will also be made among various groups, for example, treatment receivers vs. treatment avoiders; spontaneous recovery without treatment vs. recovery with treatment; non-treatment vs. comparable users in other treatment-specific samples. Among those who receive treatment, types and patterns of drug use, and treatment outcomes will be analyzed and compared to other treatment samples studied by the research group. Analyses will focus on identifying contributing factors and quantifying their relative importances for improving treatment utilization and effectiveness by applying appropriate advanced statistical models. Policy-relevant and cost- benefit analyses will be performed. Products of the study will suggest improvements for drug treatment utilization and effectiveness and will assist in planning for drug abuse treatment system improvements.