Adult male C57BL/6J inbred mice were subjected to ultraviolet radiation (UVR) exposure (302-nm peak wavelength; average intensity 282 microW/cm2) for 1 h and monitored for ocular aldehyde dehydrogenase (ALDH) and alcohol dehydrogenase (ADH) activity changes over a period of 25 days. Dramatic reductions in activities were observed by 4-6 days postexposure, resulting in enzyme levels of 15-16% of control animals. Major decreases in corneal enzyme levels were predominantly responsible for these changes. Ocular morphology was observed throughout using a photoslit-lamp biomicroscope, with maximum corneal clouding occurring at days 4-6. These data support earlier proposals for major roles for these corneal enzymes in assisting the cornea in protecting the eye against UVR-induced tissue damage.