OBJECTIVE--To review and analyse the changing incidence of gonorrhoea and the increasing antibiotic resistance in gonococci in Australia from 1981 to 1991. DESIGN--Use of data from the sample of gonorrhoea in Australia examined by the Australian Gonococcal Surveillance Programme (AGSP), a continuing long-term multi-centric study of gonococcal disease and gonococcal susceptibility to antibiotics, over the period 1 July, 1981 to 30 June, 1991. RESULTS--Over 32,000 cases and strains from defined sources were examined in the 10 year study period. The number of cases of gonorrhoea in the sample decline from a peak of 6599 in 1982-1983 to 1121 in the final year under review, a reduction of 83%. Periods when greater than average reductions in incidence occurred in different groups were noted. Ano-rectal gonorrhoea in men decreased sharply in 1985 during an overall decline of 92.5% recorded between 1 July, 1981 to 30 June, 1987. However, the incidence of ano-rectal cases in males rose in subsequent years while gonorrhoea, overall, continued to decrease and at a greater rate after 1985. Antibiotic resistance in gonococci in Australia was manifested both as a progressive increase in the levels of intrinsic resistance to the penicillins and through the appearance and spread of penicillinase-producing N gonorrhoeae (PPNG). At the end of the review period in June, 1991, 8.8% of gonococcal isolates in Australia showed high levels of intrinsic resistance to the penicillins and 13% of strains were PPNG. These separate mechanisms of resistance appeared at different times in different parts of Australia, and their importance also varied throughout the country. Most infections with PPNG were acquired by men overseas whereas most women with PPNG were infected locally. Endemic spread of PPNG was a significant problem in Sydney and Melbourne, but decreased in importance in the later years of the study. CONCLUSIONS--In the past decade a large reduction in the incidence of gonorrhoea and, by implication, other STDs has occurred in the past decade in Australia. In some groups of patients the decline in incidence is continuing while in others a slight increase has been noted. Resistance to antibiotics of gonococci in Australia was mainly restricted to the penicillins, but through both chromosomal and plasmid-mediated mechanisms. This resistance was seen particularly in Sydney and Melbourne where endemic cycles of transmission of PPNG were established, and in infected travellers from S-E Asia in other centres. Valid and comparable, and regionally relevant data are a continuing requirement for assessing and modifying antibiotic treatment regimens for gonococcal disease.