In response to the growing numbers of young people affected by HIV around the world, MTV (Music TV), the world's largest television network, has aired a global HIV prevention campaign since 1999, expanding it into a multicomponent campaign in 2002. Questions have been raised, however, about whether MTV is an appropriate channel for these messages, given its provocative content and its reach to those at the upper end of the socioeconomic scale. To address questions about who MTV reaches, viewership data were analyzed from baseline surveys conducted as part of an evaluation of the 2002 HIV prevention campaign. The two sites included in this analysis were Kathmandu, Nepal, and Sao Paulo, Brazil - each with very different cultures and media environments. We found that, in general, heavier viewers of MTV are younger, better educated, and more dependent on their parents, and they have more access to satellite television and the Internet. MTV viewing was associated with positive attitudes toward HIV prevention behaviors (except for abstinence until marriage) but not with premarital sexual activity.