We use the Nepal Adolescents and Young Adults (NAYA) Survey of 2000 to analyse the prevalence of sexual activity and risky sexual behaviour among Nepalese males aged 14-22 years. Risky sexual behaviour is considered to be characterised by having multiple partners, or having one non-regular partner with whom a condom was not used, in the 12 months before the survey. About 9 per cent of the sexually active married men aged 14-22 years, and about 20 per cent of sexually active single men in the same age group, are engaged in risky sexual behaviour. Logistic regression analysis shows that, among married men, those who are better educated and who have better educated fathers are more likely to engage in risky sexual behaviour. Among single men, risky sexual behaviour is especially likely in certain rural districts where it is tolerated by the local culture. The quantitative analysis is supported by qualitative data drawn from focus group interviews.