There have been many reports of primary Vibrio vulnificus septicemia in Korea since 1987. This study was undertaken to determine the cellular fatty acid (CFA) compositions of 95 clinical strains of V. vulnificus isolated in Korea during 1985-1995. We compared these results with the CFA profile of V. vulnificus in the Microbial Identification System (MIS) (CLIN library version 3.9; Microbial ID Inc., Newark, DE, U.S.A.), and the grouping of V. vulnificus by CFA analysis was also performed. The relationship between groups and serotypes of V. vulnificus was described. Although most of the CFAs in V. vulnificus strains were similar to the CFA profile of V. vulnificus in the MIS, some distinctive differences were observed between the results of this study and the MIS CFA profile of V. vulnificus. First, the means of 2 major CFAs, 16 : 0 and 16 : 1w7c, were 22.16 and 18.26% in this study but 23.52 and 25.44% in the MIS, respectively. Second, all isolates had 11 : 0iso3OH, which was not present in the MIS. Of 95 strains, 10 strains (10.5%) showed 'NO MATCH' results by the MIS identification. Eighty five strains (89.5%) were identified as V. vulnificus by the MIS (the first choice identification), but they disclosed low SI values of <0.6 (not 'EXCELLENT MATCH') except 2 strains (2.1%). This showed that V. vulnificus strains isolated in Korea had different characteristics in CFA composition in comparison with the MIS V. vulnificus library. Nine groups comprising all the strains were obtained by cluster analysis and were further characterized by principal-component analysis. There was heterogeneity between the groups by CFA and serotypes of V. vulnificus. The same serovars were distributed into diverse groups.