Sexually transmitted diseases (STDs) represent a major public health problem in the world and the advent and increase of human immunodeficiency virus infection during the last decade has highlighted the importance of infections spread by the sexual route. The World Health Organization estimates that the global incidence in 1995 of new cases of selected curable STDs, which are gonorrhea, chlamydial infection, syphilis and trichomoniasis, was 333 million. Control programs for STDs must prevent the acquisition of STDs, their complications and sequelae and interrupt and reduce transmission. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.