To develop a practical process for R-(-)-mandelic acid production from racemic mandelic acids, we investigated a two step microbial reaction which employs the asymmetric oxidation of S-(+)-mandelic acid by Pseudomonas polycolor IFO 3918 and the asymmetric reduction of oxidated S-(+)-mandelic acid by microorganisms. Microorganism screening was conducted for the asymmetric reduction of benzoylformic acid. Among 800 culture strains tested, microorganisms belonging to Alcaligenes, Corynebacterium, Enterococcus, Gluconobacter, Kurthia, Micrococcus and Streptomyces genera exhibited high reducing activity for benzoylformic acid derived from S-(+)-mandelic acid. Micrococcus freudenreichii FERM-P 13221 was determined to be the best, and therefore used as a biocatalyst for reducing benzoylformic acid. The optimum conditions for R-(-)-mandelic acid production were also determined. Under optimal conditions, we attempted to convert racemic mandelic acid to R-(-)-mandelic acid using P. polycolor and M. freudenreichii, both simultaneously or consecutively. For both types of reactions, the S-(+)-isomer in a racemic mandelic acid (45 g/l) solution was completely oxidized, and 31.5 g/l of R-(-)-mandelic acid were produced in the reaction mixture.