OBJECTIVES: To identify variables that distinguish patients with sexually transmitted infections (STIs) who seek care in public or private health units. GOAL: To recommend measures for improved care of patients with STIs. STUDY DESIGN: Patients with STIs were interviewed at public (n = 101) or private health units (n = 124). Information was collected on attitudinal, normative, and self-efficacy beliefs; STI symptoms; health-seeking behavior; sociodemographic characteristics, and on partner referral. RESULTS: Choosing private health units is favored by age >25 years, favorable beliefs towards private health units (e.g., they cure or prevent STIs and give adequate drug doses); unfavorable beliefs towards public health units (such as they make STIs chronic and have corrupt staff); not being influenced by sexual partner(s) in choice of treatment site, being likely to chose a treatment site if sexual partners were not treated free, and being likely to choose a treatment site if not recommend by a friend. This 9-variable model correctly classified 214 (95%) of the 225 patients (model chi squared = 192, 9 degrees of freedom, P <0.001). CONCLUSIONS: Psychosocial variables markedly influence choice of health care provider. Improving quality of care will enhance STI management and help to modify the unfavorable psychosocial beliefs.