Objectives. To analyze demographic and practice characteristics of private physicians in 10 cities of Peru, and to shed light on the role of private practice in the delivery of medical care to patients with sexually transmitted infections (STIs). Methods. As part of an interventional trial designed to improve physician management of STIs in 10 cities in Peru, detailed information was compiled regarding numbers of physicians in each city. A door-to-door survey was then conducted within each city of all private and public medical offices and institutions. Each physician encountered who had a private practice was asked to answer a questionnaire regarding demographic information, medical education, specialty, type of private and public practices currently engaged in, number of STI cases seen per month, and average earnings per consultation. Results. Of 2 060 physicians working in the 10 cities, 507 reported having a private practice, either exclusively or concurrently with other clinical positions. Almost all the private physicians (97.4%) reported managing cases of STIs. Regional differences among private physicians were found in physician density, gender, and place of medical training. In addition, significant variations by gender were seen in rates of specialization, earnings per consultation, and numbers of female patients with STIs seen per month. Conclusions. Studies of the physician workforce can provide meaningful insights for potential use in addressing public health problems. This study provides valuable information that can help understand the important role of private physicians in managing STIs in Peru.