Vibrio parahaemolyticus is a common food poisoning pathogen associated with seafood. New O3:K6 strains originating from India in 1996 were the first pandemic strains and spread rapidly throughout many Asian countries. This study examines the characteristics of these new O3:K6 strains with respect to acid susceptibility and survival competition with Pseudomonas fluorescens and indigenous oyster spoilage microflora. Results revealed that the exponential phase cultures of new O3:K6 strains were significantly more tolerant of acid at pH 3.0 than the environmental strains. In these co culture experiments, survival of the V. parahaemolyticus strains was influenced by the bacterial strains, incubation medium and incubation temperature. All V. parahaemolyticus strains showed similar survival ability when co-cultured with P. fluorescens in 1/10 tryptic soy broth. In the oyster medium, the environmental strain survived better than the new O3:K6 strains at 4 or 25ûC. Both of the new O3:K6 strains (1121 and 1137) showed similar survivability in this study. These data offer hints on the survival of the new O3:K6 strains and their ability to spread.