The national notification gonorrhoea data are analysed over the period 1976-88 in conjunction with detailed data from the two STD clinics in Amsterdam in order to get an insight into the underlying reasons for the downward trend of gonorrhoea in The Netherlands. Possible effects of variations in reporting bias, seasonality, resistance against antibiotics, and sexual behaviour on gonorrhoea rates are considered. In 1981 the incidence of gonorrhoea started to decrease, thus preceding the onset of the AIDS epidemic in The Netherlands. Since 1983 the decline in gonorrhoea further accelerated and has been most apparent among homo- and bisexual men, presumably as a result of behavioural changes because of AIDS. There is less evidence for massive (AIDS related) behavioural changes among heterosexuals. The increasing percentage of gonorrhoea patients with recurrent episodes of STDs in Amsterdam may suggest that highly sexually active individuals continue to put themselves at risk of STDs and persist in acquiring and transmitting gonorrhoea.