Since 1981 sexually transmitted diseases (STD) diagnosed at the STD clinics of the Municipal Health Service of Amsterdam, are registered by sex, sexual orientation and prostitution. Numbers of diagnoses per 1,000 new consultations are compared for each group of visitors over the period 1981-1987. Among heterosexual visitors there has been a steady decline of gonorrhoea and trichomoniasis since 1981. Genital herpes and venereal warts after increasing until 1985 have reached a plateau. Because of the early appearance of these trends they cannot be attributed to changes in heterosexual behaviour brought about by the AIDS epidemic. Nongonococcal urethritis has been increasing since 1981, possibly due to insufficient Chlamydia trachomatis detection in the country. After several years of decline, early syphilis has been increasing since 1987 among heterosexual men and women. Among homo/bisexual men the numbers of cases of gonorrhoea and early syphilis as well as the number of consultations for STD have decreased strongly since 1984, which may well be the result of changes in homosexual behaviour because of AIDS.