Aldose reductase (AR) has been implicated in the development of the diabetic complications. To discover novel treatments for diabetic complications from natural sources, 65 Korean herbal medicines have been investigated for inhibitory activities on AR. Of these, 23 herbal medicines exhibited a significant inhibitory activity compared with 3,3-tetramethyleneglutaric acid (TMG). Particularly, 8 herbal medicines, Acer tataricum (twig, stem and leaf), Acer tataricum (fruit), Rhododendron schlippenbachii (twig, stem and leaf), Weigela subsessilis (twig, stem and leaf), Acer mono (branch and leaf), Ailanthus altissima (twig, stem and leaf), Lindera obtusiloba (branch and leaf), Solidago serotina (whole plant) showed three times more potent inhibitory activity than the positive control, TMG.