About 1000 bacterial colonies isolated from sea water were screened for their ability to convert DL-5-phenylhydantoin to D(-)N-carbamoylphenylglycine as a criterion for the determination of hydantoinase activity. The strain M-l, out of 11 hydantoinase-producing strains, exhibited the maximum ability to convert DL-5-phenylhydantoin to D(-)N-carbamoylphenylglycine. The strain M-l appeared to be a halophilic Pseudomonas sp. according to morphological and physiological characteristics. Optimization of the growth parameters revealed that nutrient broth with 2% NaCl was the preferred medium for both biomass and enzyme production. D-Hydantoinase of strain M-l was not found to be inducible by the addition of uracil, dihydrouracil, beta-alanine etc. The optimum temperature for enzyme production was about 25 degrees C and the organism showed a broad pH optimum (pH 6.5-9.0) for both biomass and hydantoinase production. The organism seems to have a strict requirement of NaCl for both growth and enzyme production. The optimum pH and temperature of enzyme activity were 9-9.5 and 30 degrees C respectively. The biotransformation under the alkaline conditions allowed the conversion of 80 g l(-1) DL-5-phenylhydantoin to 82 g l(-1) D(-)N-carbamoylphenylglycine within 24 h with a molar yield of 93%.