This proposal requests renewed funding for the Center for Prevention and Treatment Methodology (CPTM) The overarching goal of the CPTM is to improve quantitative methods for behavioral research in the prevention and treatment of substance use, HIV, and related disorders, and to place the improved methods in the hands of prevention and treatment scientists. The CPTM Specific Alms of the CPTM are: (A) To develop innovative methods for design and analysis in longitudinal research on substance use, HIV risk behaviors, and closely related areas in the behavioral sciences; (B) To develop innovative methods for research that informs building individualized interventions for prevention and treatment of substance use, HIV, and related disorders; (C) To increase the relevance of the CPTM's work to research on HIV; and (D) To maintain and enhance the CPTM as a national resource playing a vital role in the fight against drug abuse and HIV. The proposed renewed CPTM will include two cores and four scientific projects. The scientific projects will develop innovative methodological approaches related to: I. Causal inference in mediation models; II. Identifying and characterizing subgroups reflecting different profiles of risk; III. Analysis of intensive (e.g. daily) longitudinal data; and IV. Empirically building adaptive behavioral interventions. The CPTM has established itself as a national resource in several ways: Our original research has been published widely in top-tier journals, both in the field of methodology and the field of substance use; we are engaged in training the next generation of methodologists, with over 30 former trainees in the work force and many more currently undergoing training; and we vigorously disseminate our methodological work in a variety of ways, including targeted publications, workshops and short courses, an information-packed web site, and free downloadable software. There is a constant and lively exchange of ideas among CPTM scientists, resulting in a high level of synergy. We are engaged in a variety of collaborative projects with drug abuse and HIV/AIDS scientists outside of the CPTM. In short, we are able to advance the field of prevention and treatment methodology very effectively by operating as a P50 center.