Substance abuse and HIV infection are a domestic health syndemic that compromises universal test-and-treat approaches for preventing HIV transmission and precipitates calls for quality improvement across the HIV Care Continuum. Dissemination of an empirically-supported behavior therapy to prompt HIV testing in addiction care settings is a large-scale effort, but with benefits attenuated by substance abusers' poor clinic attendance and antiretroviral (ARV) therapy adherence. Thus, expanded transport of available empirically-supported behavior therapies to HIV care settings is needed to pre-empt such care disengagement. To identify a candidate therapy compatible for HIV care, one must consider with whom and with what intent the HIV workforce is to intervene. Extant prevalence rates for substance use disorders (SUDs) among HIV care enrollees are drawn from single- site trials, and vary by selected patient demography and history. Corresponding sample sizes often preclude analysis at a substance-specific level, even as some substances carry distinct considerations for transmission and course of HIV. Likewise, single-site trials evaluating impacts of substance abuse on patient adherence and response to HIV care offer limited generalizability. Fortunately, a coordinated multisite HIV care repository, governed by Center for AIDS Research Network of Integrated Clinical Systems (CNICS), incorporates data from sites across the U.S. and offers opportunity to determine the scope and impact of substance-specific SUDs in a large, diverse population of patients linked to HIV care. Proposed analyses will focus on care engagement, defined as a two-year period following HIV diagnosis and linkage to care. An available CNICS sample of ~10,000 patients will enable computation of broadly representative prevalence rates for substance- specific SUDs and comparisons of such SUD subgroups to non-SUD patients on key outcomes like cumulative viral burden, clinic attendance, ARV adherence, health risks, and quality-of-life. Relative to non-SUD counterparts, SUD subgroups are expected to exhibit greater viral burden, poorer clinic attendance and ARV adherence, more health risks, and lesser quality-of-life. In response to NIDA PA-12-282 (AIDS-Science Track Award for Research Transition), a New Investigator to HIV Research proposes to complement these CNICS- based analyses by gathering of dissemination-focused data during site visits to regional HIV care clinics. Data will be collected from site directors and direct-car staff via mixed-method procedures, with intent to identify from among NIDA-endorsed candidate behavior therapies an approach perceived as contextually-compatible. This low-cost, high-yield approach will advance knowledge of the SUD-HIV syndemic, and inform a future R01 testing implementation of an empirically-supported behavior therapy to engage substance abusers in HIV care.