The primarily heterosexual character of AIDS transmission in sub-Saharan Africa, a context where men are dominant in sexual and reproductive arenas, makes it important to understand male behavior in sexual and related health matters. The relationship between misperceptions about HIV/AIDS and be- havioral responses to knowledge about the disease, in this case, condom use, is examined among married Kenyan men interviewed in the 1993 Demographic and Health Survey (DHS). The focus on the extent to which (mis)perceptions influence behavior, net of AIDS-related knowledge, reveals a significant in- teractive effect of knowledge and perceptions on condom use. This finding provides a basis for arguing a rationality for health, and indeed other, behav- iors that otherwise appear irrational. The findings also have implications for specific aspects of AIDS-related knowledge that are imparted to communities and individuals, as well as for how we examine other health-related behaviors such as smoking and drunk drivi