In penicillinase-producing Neisseria gonorrhoeae (PPNG), resistance to penicillin may be mediated by one of several related plasmids of different sizes. These include the Asian, African and Rio/Toronto plasmids. Identification of these plasmids provides useful epidemiological information, but has necessitated plasmid purification and gel analysis. We have developed a rapid, simple multiplex polymerase chain reaction (PCR) which discriminates between the beta-lactamase resistance plasmids that are frequently found in strains of N. gonorrhoeae. Amplicons of 1191, 958 and 650 bp were produced from strains containing the African, Asian and Rio/Toronto plasmids, respectively, whilst no products resulted from non-PPNG strains harbouring the cryptic, conjugative or tetracycline resistance plasmids. PCR analysis of 123 strains of PPNG identified 60 strains with African, 16 strains with Asian and 47 strains with Rio/Toronto plasmids and showed complete agreement with the standard plasmid analysis.