Introduction: The use of the Internet to meet sexual partners has been associated with human immunodeficiency virus (HIV) transmission and a syphilis epidemic in men who have sex with men (MSM). People who seek sex through the Internet also tend to use this resource to search for information about sexually transmitted infections (STI). Almost all the studies related to the Internet and HIV/STI come from developed countries, where factors such as the place and cost of access are different than in developing countries. Objective: To evaluate the use of the Internet for seeking sex partners and information on STIs among persons living with HIV. Methods: We conducted a cross-sectional study among clients of the Vía Libre Clinic, an HIV treatment center in Lima, Peru, between May and June of 2004. Results: 100 HIV-positive persons (64 men and 36 women) were interviewed after written informed consent was obtained; 59% reported using the Internet in the last 12 months. Of these, the majority (73%) accessed the Internet at a 'cabina pública', 16 (27.1%) reported having gone online to search for sexual partners and 5 (8.5%) reported having sex with a partner they found over the Internet. Internet sex-seeking was significantly more common among men who have sex with men (MSM; 15/16, or 94%) than among men who have sex with women (MSW; 1/16, or 6%; P = 0.032). All 5 participants (100%) who reported having sex with a partner found online were MSM. No women reported having sought sex partners via the Internet. 76% (45/59) of the HIV-positive persons who had accessed the Internet in the past year used it to find information on HIV and 39% (23/59) to seek for information on other STIs. Among those who used the Internet to meet sex partners, 87.5% (14/16) also sought information related to HIV, compared to 72.1% (31/43) of persons not seeking partners (P = 0.31). Discussion: Among HIV-positive persons who attend our clinic, more than half reported access to the Internet. The majority use the Internet to look for information about HIV/AIDS, and more than a quarter, almost exclusively MSM, use it to search for sex partners. These findings suggest that the Internet is a convenient tool to engage high-risk men with online HIV/STI prevention.