As for several other infectious diseases, sexually transmitted diseases (STD) in many developing countries are characterized by a high incidence and prevalence, a high rate of complications and sequelae (particularly in women and neonates), a different clinical spectrum (more genital ulcer disease), and a severe problem of antimicrobial resistance (in N. gonorrhoeae and C. trachomatis). In Africa, HIV is mainly spread heterosexually, resulting in a major problem vertically acquired HIV infection in children. STDs, in particular those associated with genital ulceration, are enhancing the efficiency of sexual transmission of HIV, and their high prevalence may partly explain the occurrence of a major heterosexual epidemic of HIV in Africa, as opposed to Europe. Factors contributing to the spread of STDs are to a large extent demographic, sociobehavioural and medical such as a larger pool of adolescents and young adults, prostitution, urban migration, indiscriminate use of antibiotics and inadequate medical facilities and STD control programmes. Programmes for the prevention and control of STD and AIDS should be an immediate priority in many developing countries.