The present invention relates to a method for producing .alpha.-hydroxy acids using an enzyme catalyst having nitrilase activity. More specifically, the invention pertains to use of Acidovorax facilis 72W (ATCC 55746) nitrilase to hydrolyze glycolonitrile to glycolic acid. Glycolonitrile is reacted in an aqueous mixture with a catalyst having Acidovorax facilis 72W nitrilase activity to give glycolic acid selectively, and at high concentration and high yield.