An understanding of all aspects of sexual behaviour is essential to the development of effective approaches to HIV prevention. Sex, Gay Men and AIDS reports on the largest empirical study of male homosexual behaviour in the UK since the work of Schofield in the 1960s. It contains findings from Project SIGMA - which is the major British study of this kind in the AIDS field, funded by the Department of Health and the Medical Research Council. Using both quantitative and qualitative analysis, the authors have developed important new theories about sexuality, which expose unhelpful stereotypes about male homosexuality and challenge outdated theories and assumptions about AIDS.