BACKGROUND: Men who have sex with men (MSM) have the highest HIV prevalence in Peru, yet they are underserved by traditional preventive programs. In Peru, the Internet and mobile phones have emerged as an effective and convenient tool to reach this population. METHODS AND FINDINGS: From October 2010 to February 2011, we conducted eight focus groups with gay identified MSM (closeted and out-of-the-closet) and with self-identified heterosexual MSM in order to identify key features and preferences to be used to tailor culturally-appropriate messages that could be delivered through Internet and mobile phones to motivate MSM to get tested for HIV. Participants reported that in order to motivate HIV testing among MSM, interventions need to be based on motivational messages that encourage participants to overcome the fear of getting tested. Messages should increase the HIV risk perception (of participants who do not consider themselves at risk) by eliciting risky situations experienced by MSM. Messages should emphasize confidentiality, respect and the professionalism of the personnel conducting the counseling and testing. A thorough explanation of the process of HIV testing and the steps to follow after receiving the results should be provided. Messages should also contain information about the venue where the test will be conducted in terms of client characteristics, location, hours of operation and personnel. Finally, stigmatizing and stereotyping messages or images about "being gay" should not be included, as they act as deterrents for getting tested. CONCLUSIONS: Interventions aimed at motivating HIV testing among MSM should include motivational messages that reduce the fear of getting tested and increase the risk perception of participants. They should also market the venue where the testing will be conducted, the professionals who will perform the tests, and the type of tests available. Stigmatizing messages or images should be avoided.