The aim of this study was to analyze the rates of condom use among military and police populations in Peru, focusing on differences in use by type of partner. A Knowledge Attitudes and Practices survey was conducted among 6,808 military and police personnel in 18 Peruvian cities between August-September 2006 and September-October 2007. A total of 90.2% of the survey respondents were male; mean age was 37.8 years and 77.9% were married/cohabiting. In all, 99.5% reported having had sex; 89% of the participants had their last sexual contact with their stable partner, 9.7% with a nonstable partner, and 0.8% with a sex worker. Overall, 20.4% used a condom during their most recent sexual contact. Reasons for nonuse of condoms included the following: perception that a condom was not necessary (31.3%) and using another birth control method (26.7%). Prevention efforts against sexually transmitted diseases should focus on strengthening condom use, especially among individuals with nonstable partners. © The Author(s) 2012.