A gas chromatographic method using a capillary column for rapid identification of Vibrio vulnificus was examined in a collaborative study. Identifications were performed by analysis of cellular fatty acid profiles which were automatically searched against reference profiles stored in a computer-generated library. Each of the 13 collaborators was sent 15 unknown isolates, which included 10 V. vulnificus isolates and 5 negative control isolates. Each collaborator was furnished with a computer-generated library, developed by the Dallas U.S. Food and Drug Administration laboratory, which contained entries for V. vulnificus, V. cholerae, V. fluvialis, V. parahaemolyticus, V. mimicus, and Aeromonas hydrophila. Of the 195 isolates sent to the collaborators, results for 190 isolates were received. The other 5 isolates were nonviable before analyses began. Of the 126 V. vulnificus isolates analyzed, 118 (93.7%) were correctly identified. Of the 65 negative control isolates sent, one was nonviable, one was misidentified as V. vulnificus, and 2 were misidentified as V. parahaemolyticus. Of the 64 negative controls analyzed, 95.3% were correctly identified. Statistical analysis shows a sensitivity rate of 0.872, specificity rate of 0.982, false positive rate of 0.010, and false negative rate of 0.206. The gas chromatographic method for identification of Vibrio vulnificus by microbial fatty acid profile has been adopted first action by AOAC INTERNATIONAL.