Background: Correct and consistent condom use is an effective strategy to reduce the risk of sexually transmitted infections (STIs). This study examines sociodemographic, behavioral, and psychosocial characteristics of 3 groups of adolescent males: consistent, sporadic, and non-condom users. Methods: The sample consisted of 931 sexually experienced male high school students in Nairobi, Kenya. Cross tabulations and general linear models were used to test the relation between each explanatory variable and condom user group. Results: Fifty-three percent of respondents reported having used condoms. Compared with nonusers and sporadic users, consistent users engaged in sexual intercourse for the first time at an older age and reported higher condom use self-efficacy, more positive peer attitudes toward safe sex, and stronger attitudes toward condom use. Compared with sporadic and consistent users, nonusers reported fewer sexual partners, less substance use, and more frequent intercourse with non-romantic partners. Sporadic users, compared with the other 2 groups, had more sexual partners and stronger attitudes that support that males and females have separate roles. The 3 groups did not differ in HIV/AIDS knowledge. On average, respondents responded correctly to two thirds of the questions. All groups perceived their risk of contracting an STI as low, and this perception did not differ by condom use. Differences in participants' age by group were minimal. Conclusions: The study supports the need for interventions that target specific condom use groups. (Contains 3 tables.)