Since early-on in the epidemic, there has been much interest in the role that bisexual behaviour among men may play in HIV transmission. This text reviews from an international perspective what has been learned about male bisexuality in countries as diverse as Peru and Britain. Its authors examine the forms that bisexuality takes in different cultures, what it means to the men concerned, and whether or not such behaviour poses special risks. The implications of such enquiry for HIV prevention efforts are also examined.