Female sex workers (FSW) are at high risk of acquiring sexually transmitted infections (STIs), including HIV, and putting their clients and other partners at risk for infection. There is considerable evidence that Social Cognitive Theory (SCT)?based interventions are effective in reducing high-risk sexual behavior among at-risk populations in the United States. However, no studies have been undertaken of such interventions with FSWs in Mexico, where high rates of STIs exist and where sex tourism attracts a large number of American clients. This article describes the development of a culturally relevant sexual risk reduction intervention based on SCT and Theory of Reasoned Action for FSWs in Mexico. The intervention was designed to promote consistent use of condoms with clients. Spanish-speaking counselors used motivational interviewing techniques and skill-building exercises to promote behavior change in a clinic-based sample of FSWs. The authors describe the intervention and provide pilot data that demonstrate the feasibility and benefits of this approach.