Background Sexual networking in popular tourist destinations is a problem worldwide. In Peru, locals sexually interacting with travelers bridge high-risk groups, the general population, and travelers. Methods A cross-sectional study was conducted in Cuzco about sexual behavior among young Peruvians who admitted having sex with travelers. A subgroup of the participants had serologic testing for Chlamydia trachomatis, Herpes simplex virus (HSV) type 2, and Treponema pallidum. Results Eighty-eight subjects volunteered for blood sampling. Their mean age was 22.9 years (±4.1) and 53.4% were male. The majority were single (86.2%), but 12.6% had a stable relationship. The median number of sexual partners in the 3 months prior to the study was 2 [interquartile range (IQR): 1-4]. During that period, 43.1% reported foreign partners, 28.4% reported foreign and Peruvian partners, 17% reported Peruvian partners, and the remaining 11.5% reported combinations of Peruvian, foreign, and sex workers partners. The median number of foreign partners in the 12-month period prior to the study was 4 (IQR: 2-8). Only 25.3% reported consistent condom use. Alcohol (69%) and drugs (36.8%) were commonly used before sexual activity. Seventy-eight percent tested positive for HSV type 2, 25% for C trachomatis, and 1.1% for T pallidum. Conclusions The core group of young Peruvians we report on demonstrated a high-risk sexual behavior and a high prevalence of sexually transmitted infections. Our results underscore the need for education on safer sex practices among this group and among travelers. © 2009 International Society of Travel Medicine.