Three strains were isolated from cultured aquatic organisms. They were Gram-negative, oxidase-positive, motile, fermentative, arginine dihydrolase-positive, lysine and ornithine decarboxylase-negative and sensitive to vibriostatic agent O/129. These strains differ from other related Vibrio species by several phenotypic features, which include acetoin and indole production and utilization of amygdalin and D-mannitol. Comparison of 16S rDNA sequences showed a close relationship to the recently described species Vibrio kanaloae (96.6 %) and Vibrio pomeroyi (96.4 %) and to Vibrio furnissii (96.6 %), but DNA-DNA hybridization experiments showed that the three isolates form a tight novel species with </=30 % DNA-DNA similarity to its closest phylogenetic neighbours. Vibrio pacinii sp. nov. is proposed, with LMG 19999(T) (=CAIM 530(T)=STD3-1057(T); DNA G+C content, 44.9 mol%) as the type strain.