The purpose of the study was to investigate the mechanisms by which UV-A at 365 nm causes damage to the eye lens. Bovine lenses were placed in special culture cells and were oriented so that the anterior surface faced the incident UV-A radiation source. The lenses were maintained in the cells during irradiation. After 5 days in culture, samples of lens epithelium, cortex, and nucleus were taken for biochemical analysis. Transglutaminase activity in the lens was affected by the radiation and showed increased activity in the lens cortex and nucleus. Specific lens protein, betaB1 crystallin (one of the enzyme substrates), was analyzed by SDS polyacrylamide gel electrophoresis and immunobloting with specific antibodies. The crystallin was affected as was shown by the appearance of degradation products. There is correlative information but no clear proof that transglutaminase is involved in the mechanisms by which UV-A causes damage to the eye lens.