The introduction of a new, fully automated system into the clinical microbiology laboratory contributes to a rapid identification of microorganisms with accurate and reliable results, but such a system requires a high cost and additional tests for identification of some species. For instance, additional tests on oxidase, indole, motility, hemolysis, and pigmentation are needed in the correct identification by using Vitek GNI+ system (bioMerieux Vitek Inc., MO, USA). In particular, Vibrio and Aeromonas species are occasionally identified incorrectly when an automated system is used, and thus conventional biochemical tests may be more reliable in the identification of such species. We experienced three cases of incorrect identification of Vibrio parahaemolyticus, Vibrio cholerae, and Aeromonas veronii biovar sobria as Vibrio alginolyticus by using Vitek GNI+ card. (Korean J Clin Microbiol 2005;8(1):99-104)