To explore the correlation of outer membrane protein I (PI) type and auxotype to clinical expression of infection with Neisseria gonorrhoeae, we characterized nutritional requirements by auxotyping and PI serovars by coagglutination assay with monoclonal antibodies of 325 consecutive clinical isolates of N. gonorrhoeae. The clinical status of each infected individual was determined by chart review. The predominant auxotype required proline, citrulline, and uracil with or without hypoxanthine (Pro-Cit-Ura-[Hyx-]) and accounted for 22% of all gonococcal strains. Pro-Cit-Ura-(Hyx-) strains were recovered from seven of 15 men with asymptomatic urethral infections (P less than .01). Of the 325 strains, 33% were PIA and 67% were PIB serovars. All five isolates in disseminated gonococcal infection were PIA serovars (P less than .01). Three percent of 168 urethral infections in men were complicated by epididymitis, and 17% of 135 cervical infections in women were complicated by pelvic inflammatory disease (P less than .0005). Neither of these complications was associated with a particular auxotype or PI serovar.