Sixty marine water samples were collected from various coastal sites around Port Blair at different times during August 1996 to July 1997. The specimens were subjected to standard procedure for isolation and identification of V. parahaemolyticus. Forty four V. parahaemolyticus isolates were detected from these specimens and all showed clear haemolysis on Wagatsuma agar plates. The haemolytic activity was abolished by heating the culture supernatants at 60 degrees C for 10 min and enhanced when plates were kept at 4 degrees C. When isolates were subjected to PCR assay for tdh gene, only one showed the presence of the gene. The results indicate the existence of pathogenic V. parahaemolyticus in the marine environment of these islands.