The anticataractogenic potential of γ-glutamylcysteine ethyl ester was investigated in model cataracts induced by L-buthionine sulfoximine. Subcutaneous injection of the ester (0.625–2.5 mmol/kg) effectively inhibited cataractogenesis in suckling mice. Treatment of mice with L-buthionine sulfoximine alone resulted in a marked reduction of the glutathione content in the eyes. This deprivation of glutathione was mitigated, to a significant degree, by coadministering γ-glutamylcysteine ethyl ester. In an experiment with rat lens in culture, γ-glutamylcysteine ethyl ester was found to elevate the lenticular level of glutathione. These results indicate that γ-glutamylcysteine ethyl ester is able to permeate across biomembranes and serves as an excellent precursor for glutathione biosynthesis, thereby exerting its anticataractogenic activity.