ObjectiveTo assess the likely impact on HIV incidence of increased condom use, a reduction in casual sexual partners, treatment programmes for other sexually transmitted diseases (STD), and combinations of these in rural Uganda.MethodsA simulation model for the transmission dynamics of HIV infection, and STD was employed, drawing on data from a rural population cohort in South-West Uganda with an HIV prevalence of 9% among adults in 1990.ResultsFor the scenario most consistent with data from the study population, 39% of all adult HIV infections were averted, in the 10 years from 1990, when condoms were used consistently, and effectively by 50% of men in their contacts with one-off sexual partners (such as bar girls, and commercial sex workers). Reducing by 50% the frequency of men's sexual contacts with one-off partners averted 68% of infections. Reducing by 50% the duration of all STD episodes averted 43% of infections. Combining these three interventions averted 82% of all adult infections in the 10 years from 1990.ConclusionA substantial proportion of HIV infections may be averted in general populations through interventions targeted only on less regular sexual partnerships.