Various microorganisms were screened for their ability to produce 2-ketobutyric acid (2-KBA) from 1,2-butanediol (1,2-BD). Among them, Rhodococcus equi IFO 3730 was selected as the best strain. The various culture and reaction conditions were optimized using this strain. Limitation of thiamine in the growing medium was found to be effective. The resting cells of the strain grown on 1,2-propanediol as the carbon source yielded 15.7 g/l of 2-KBA from 20 g/l of 1,2-BD after 32 h incubation at 30 degrees C in the reaction mixture under optimal conditions.