OBJECTIVES: To determine baseline characteristics of an occupational cohort of women in Mwanza City, Tanzania, and factors associated with reattendance at 3 months, in preparation for a microbicide trial. STUDY DESIGN: One thousand five hundred seventy-three women aged 16-54 years working in food outlets and recreational facilities were enrolled, interviewed, and examined at community-based reproductive health clinics, provided specimens for HIV/STI and pregnancy testing, and attended 3 monthly clinical follow-up. RESULTS: Baseline prevalence of HIV was 25.5%; pregnancy 9.7%; herpes simplex virus type-2 74.6%; active syphilis 10.2%, bacterial vaginosis 52.6%; gonorrhea 5.5%; chlamydia 5.9%; and trichomoniasis 12.3%. Reattendance at 3 months was 74.1% and was higher in older women, less mobile women, and in those who received an HIV-negative result at enrollment. CONCLUSIONS: Baseline characteristics of this occupational group suggest their suitability for microbicide trials. A screening round, locally appropriate informed consent procedures, and effective community tracing may help reduce losses to follow-up in such settings.