We carried out auxanographic typing and plasmid identification on 1380 isolates of penicillinase producing Neisseria gonorrhoeae (PPNG) isolated in the Netherlands in 1982 and found four plasmid patterns and 24 auxotypes with noticeable local or regional variations. Among 756 strains harbouring the 3 X 2 megadalton (Mdal) resistance plasmid ("African" type), with or without the 24 Mdal transfer plasmid, 667 (88%) were non-requiring and inhibited by phenylalanine. This type was endemic in most of the cities or regions we studied. Twenty methionine requiring PPNG strains were found, all harbouring the 3.2 and 24 Mdal plasmid; virtually all of them were isolated or contracted in the region of Groningen. The predominant (443 (71%) auxotype among the 624 PPNG strains containing the 4.5 Mdal plasmid ("Asian" type) (with or without the 24 Mdal plasmid) was proline requiring. This auxotype (with the 4.5 Mdal and 24 Mdal plasmid) caused an outbreak in Amsterdam, and in Groningen replaced the local methionine requiring auxotype which had the 3.2 Mdal and 24 Mdal plasmids. Many auxotypes with the 4.5 Mdal plasmid, and requiring proline only, or proline and isoleucine, circulated in the Hague. Spread of imported strains by prostitution played an important part in the epidemiology of infection with PPNG strains.