Latino Family Services' (LFS) Outreach and Pre-Treatment Program (OPT) has a mission to increase access of high-risk individuals to substance abuse treatment and HIV/AIDS and related services, and to decrease high-risk behaviors related to HIV/AIDS, TB and/or substance abuse. This mission is addressed through three program components: (1) outreach to high-risk individuals; (2) assessment and referral to needed services; and (3) facilitation of substance abuse pre-treatment didactic and support groups. Part of the OPT's evaluation involved tracking and interviewing clients three and six months after the intake assessment. This paper discusses methodological challenges faced by the evaluator in longitudinal tracking and interviewing a bicultural high-risk population. Recognizing the diversity of the target client population, we developed a culturally sensitive approach to tracking and interviewing Hispanic clients. This included: locating a bilingual/bicultural research interviewer; translating the questionnaire into Spanish; conducting the interviews in Spanish when preferred by the client; identifying effective incentives for participants; and tracking clients in a culturally-sensitive manner. We also describe the approach taken to maintain the methodological rigor of the evaluation. This included: maintaining the objectivity of the interviewer; maintaining the independence of the research interviewer from job roles of program staff; and protecting client confidentiality. Finally, the problems associated with tracking and following-up with this high risk client group are described, as well as the outcomes of such efforts.