The present invention relates to novel hydantoin derivatives, processes for producing said hydantoin derivatives, pharmaceutical compositions containing at least one of said hydantoin derivatives as aldose reductase inhibitors and novel intermediate compounds in the synthesis of said hydantoin derivatives. The present invention is based on the selection of a hydantoin which is bonded by a sulfonyl group to various substituents at the 1-position of the hydantoin skeleton. The compounds of the present invention have a strong inhibitory activity against aldose reductase. These compounds are extremely useful for the treatment and/or prevention of various forms of diabetic complications based on the accumulation of polyol metabolites.