Recent developments in the epidemiology of sexual transmitted diseases (STD) in developing countries are reviewed. STD are very frequent in the tropics, particularly in large urban areas. They put a heavy burden on public health because they affect the economically most important age groups and because their sequellae may be fatal. Pelvic inflammatory disease and its consequences, and morbidity during pregnancy and the neonatal period are among the most important causes of mother and child morbidity. STD favour sexual transmission of HIV and may therefore explain the explosive AIDS epidemics in many developing countries. Antimicrobial resistance has made treatment of gonorrhoea and chancroid more difficult and more expensive. STD and HIV infection may be responsible for up to 17% of productive years lost to disease in certain regions. Strategies to control STD should be developed and linked with the AIDS programs. Both should be integrated in the primary health care system.