For the optical resolution of R-(-)-mandelic acid from (+/-)-mandelic acid, Pseudomonas sp. MA02, which assimilated S-(+)-mandelic acid as carbon and energy source, was isolated from soil. Using the fed-batch culture under optimal condition, R-(-)-mandelic acid was accumulated up to the maximum theoretical yield of 50% (30 g l(-1)) and entiomeric excess of 99.4%.