The association between perception of risk of HIV infection and sexual behaviour remains poorly understood, although perception of risk is considered to be the first stage towards behavioural change from risk-taking to safer behaviour. Using data from the 1998 Kenya Demographic and Health Survey, logistic regression models were fitted to examine the direction and the strength of the association between perceived risk of HIV/AIDS and risky sexual behaviour in the last 12 months before the survey. The findings indicate a strong positive association between perceived risk of HIV/AIDS and risky sexual behaviour for both women and men. Controlling for sociodemographic, sexual exposure and knowledge factors such as age, marital status, education, work status, residence, ethnicity, source of AIDS information, specific knowledge of AIDS, and condom use to avoid AIDS did not change the direction of the association, but altered its strength slightly. Young and unmarried women and men were more likely than older and married ones to report risky sexual behaviour. Ethnicity was significantly associated with risky sexual behaviour, suggesting a need to identify the contextual and social factors that influence behaviour among Kenyan people.