The Neisseria gonorrhoeae porin protein (Por) is a potential vaccine target and is the antigenic determinant for serovar typing. Two classes of Por, PIA and PIB, and antigenically distinct variants within each class result from sequence variations in the por gene variable regions (VRs) encoding surface-exposed loops. Oligonucleotide probes to 5 VRs of each class were used in checkerboard hybridizations to type 282 clinical gonococcal isolates selected from strains collected over the course of 10 years. PIA strains (n=63) showed limited por diversity, with 90% having 1 of 4 por types. PIB strains (n=219) were more diverse, although several common por types were identified that persisted over time. Variation within individual VRs was found to be limited. The present study provides information about the diversity of Por in strains circulating in a single geographic region over time, illustrates the utility of a novel por typing method, and has implications for vaccine development.