We analysed 467 isolates of Vibrio parahaemolyticus for possession of tdh/trh gene in comparison with urease production and serotypes. Strains possessing tdh+/trh-, tdh+/trh+, tdh-/trh-, and tdh-/trh- show positive urease production 2.1, 100, 65.7, 100%, respectively. Serotypes of O1:K69, O3:K6, O3:K72, O6:K18, O6:K46 and O1:KUT were frequently positive (100% except 91.7% of the latest one) in urease production. All isolates of O3:K6 prossessed trh, whereas all isolates of certain serotypes including O1:K69 and O3:K72 possessed both trh and trh and tdh genes. Among these, most of O1:K69 and O3:K72 were urease producer. From these results, we speculate that urease production is closely related to the presence of the trh gene or/and lesser production of TDH. We also found the new combination of serovar, O3:K25, O4:K37 and O13:K72 in Kanagawa phenomenon-positive strains.