Between 1976 and 1984 204 infections by penicillinase-producing Neisseria gonorrhoeae (PPNG) were seen in the Whitechapel Clinic. In 1984 PPNG were isolated from 4.7% of all patients attending with gonorrhoea. Three infections were homosexually acquired; 140 infections (68%) were acquired in the U.K. Strains that were tested were fully sensitive to spectinomycin (190), cefuroxime (177), kanamycin (170), amoxycillin combined with clavulanic acid (24) and rosoxacin (18). Of 135 strains 61% were resistant to co-trimoxazole, 69% of 169 to tetracycline (MIC greater than or equal to I mg/l) and 32% of 75 to streptomycin. Of 109 strains subjected to plasmid typing, 72(66%) were Asian strains. Of these, 55 (50% of the total) were without and 17 (16% of the total) possessed the 24.5 Mdal transfer plasmid; 27 (25%) were African strains without and 10 (9%) with the transfer plasmid. Of the Asian strains 10 were acquired in Africa. All four plasmid-containing strains are now endemic in the U.K. On the basis of the sensitivity tests, spectinomycin, cefuroxime and kanamycin should be effective in treatment, but not co-trimoxazole and tetracycline.