Six strains of Vibrio parahemolyticus isolated from diarrheal patients and the 12 strains from sea water were serotyped and analyzed for biocnemical characteristics, antibiotics sensitivity and detection of toxR, gyrB, tdh, and trh genes. Arbitrarily-primed polymerase chain reaction method were performed on the 6 strains from patients and the following results were obtained. 1. The Vibrio parahemolyticus isolated from patients were belonged to 5 different serotypes: O4:K8, O4:KUT, O6: K18, O10:K71 and O3:K6, but those isolated from sea water were belonged to 5 different serotypes: O1:KUT, O2:KUT, O3:K45, O4:K37 and OUT:KUT. All strains explained have different serotypes depending on the different source. 2. Three serotype (O4:K8, O4:KUT, O6:K18) isolated from patients were positive for the urease hydrolysis, whereas only one strain of serotype O1:KUT isolated from sea water was positive to the same. Furthennore, the serotype O6:K18 (1 strain) was positive for the fermentation of dulcitol. Both toxR and gyrB genes were detected from all strains isolated. 3. As for control the 2 strains of serotype O3:K6 and 6 strains isolated from patients, serotype O3:K6 were resistant to oxacillin, penicillin, vancomycin. All strains were sensitive to chloramphenicol and tetracycline yet the antibiogram type showed 6 groups from I to VI. 4. DNA probe hybridization method was used to detect genes. The trh1 was detected both from serotype O4:KUT and O6:K18 isolated from patients and the trh2 was also detected from one strain from each O10:K71 and O1:KUT isolated from patients and sea-water respectively. The tdh gene only was detected from two strains of O3:K6 isolated from patients of 1998. The tdh, trh1 and trh2 were not detected from 7 strains out of 12 strains isolated from sea water whereas the production titer of TDH isolated from patients showed from 2048 times to 4096 times. 5. Four strains of the serotype O3:K6 isolated from Korea, India and Japan as well as 3 strains from Korean patients were tested by AP-PCR to classify serotypes. As for its result the amplicon showed the same in the 4 strains of the serotype O3:K6 whereas the four strains of different serotype from patients are so difference as to explain no interrelations at all. The result explains that the serotype O3:K6 is the same genes regardless from where it is isolated.