Following the isolation of the first penicillinase-producing gonococcus in 1976 the number of such isolates rose rapidly in the United Kingdom until 1982. There was a smaller increase in 1983. At St. Thomas' Hospital, the largest clinic serving the population of South London, there was a parallel rise with stabilisation from 1982 to 1984. While for some years relatively more infections diagnosed at St Thomas' Hospital appeared to originate abroad than in the country as a whole, this proportion has gradually declined to approximately the national figure. With a gradual decline in the total numbers of gonococcal infections in the United Kingdom the proportion of infections by PPNG has continued to rise. It is important to monitor this closely, to review therapy recommendations where indicated and to maintain a vigilant watch for local epidemics.