BackgroundAfter many years of decline, the incidence of gonorrhea in Sweden reached an all-time low of 2.4 cases per 100,000 inhabitants in 1996; however, the incidence has been increasing since 1997.GoalTo describe the reemergence of gonorrhea in Sweden using clinical epidemiologic data and microbiologic characterization of isolated strains ofNeisseria gonorrhoeae.Study DesignN gonorrhoeaestrains isolated in Sweden from February 1998 to January 1999 were serotyped and an epidemiologic data questionnaire was sent to each clinician reporting a case of gonorrhea.ResultsEpidemiologic and microbiologic data were obtained for 357 cases (91% of all cases diagnosed during the period). Domestic cases had significantly increased since 1997. Serovar IB-3 was the most common isolate in domestic cases of heterosexually exposed teenagers, and serovar IB-2 was the most frequent isolate in domestic cases of homosexually exposed men. Of the imported cases, 47% were exposed in Asia and 6.5% were exposed in Eastern Europe.ConclusionThe increase of gonorrhea in Sweden is due to an increase of domestic cases. Heterosexual teenagers and homosexual men were identified as core groups infected by different serovars ofN gonorrhoeae.