Using an ecological model, we describe substance use and sexual risk behaviors of young male laborers at a roadside market in Malawi. Data included observations and interviews with 18 key market leaders and 15 laborers (ages 18-25 years). Alcohol, marijuana, and commercial sex workers (CSWs) were widely available. We identified three patterns of substance use: 6 young men currently used, 6 formerly used, and 3 never used. Substance use was linked to risky sex, including sex with CSWs. The market supported risky behaviors through availability of resources; supportive norms, including beliefs that substance use enhanced strength; and lack of restraints. Community-level poverty, cultural support for alcohol, interpersonal family/peer influences, early substance use, and school dropout also contributed to risky behaviors. Parental guidance was protective but not often reported. Local programs addressing substance use and risky sex simultaneously and better national substance use policies and mental health services are needed.