BACKGROUND: V. parahaemolyticus O3:K6 strains responsible for the increase in the number of cases of diarrhea in Southeast Asia since 1995. We performed serotyping of V. parahaemolyticus isolated from different geographic areas in Korea since 1998. METHODS: A total of 45 V. parahaemolyticus strains were isolated from clinical specimens of pa-tients with diarrhea in different geographic areas of Seoul (Hanyang University Hospital, 16 cases), Incheon (Gachon Medical Center, 27 cases) and Gwangju (Chonnam University Hospital, 2 cases) from 1998 to 2000 in Korea. Serovar O3:K6 of V. parahaemolyticus was determined by slide and tube agglutination tests with specific antisera (Seiken, Japan). RESULTS: The twenty-eight (62%) of 45 samples were positive to specific antisera of V. parahae-molyticus O3:K6. The O3:K6 strains were detected 11/16 (69%) in Seoul, 15/27 (56%) in Incheon, and 2/2 (100%) in Gwangju. V. parahaemolyticus O3:K6 was detected 11/16 (69%) in 1998, 12/18 (67%) in 1999, and 5/11 (45%) in 2000, respectively. CONCLUSIONS: We report the epidemic emergence of V. parahaemolyticus O3:K6 in Korea, since 1998.