The effect of large intake of dietary ascorbic acid on heat-induced eye lens protein damage has been studied. Male guinea pigs of the Hartley strain were used. Ascorbic acid was administered to the experimental animals in the drinking water. The mean daily ascorbic acid intakes for the control and experimental animals were 10 and 366 mg/kg body weight, respectively. The ascorbic acid level in the lens of the experimental animals was significantly higher than in the controls, but no differences in the content of water-soluble lens proteins were observed. When a solution of water-soluble protein was incubated at 60 ° C, insoluble aggregates were formed. The loss of water-soluble proteins from the lens of the experimental animals was significantly less than that of the controls. The results indicated that large quantities of dietary ascorbic acid were able to protect lens constituents against heat-induced damage.