Age- and gender-related changes in malondialdehyde (MDA) levels, superoxide dismutase (SOD) and catalase (CAT) activities in rat livers exposed to different doses of whole-body gamma-ray radiation were determined. In addition, the effects of exogenous glutathione (GSH) against radiation injury in rat livers were investigated. We found that MDA levels have an age-associated increment and an increasing radiation dose-related elevation, although they decrease slightly in the 4 Gy group. The MDA levels in old rats were lower in males than in females, while those of young rats did not change. There were no observed age-related changes in SOD activities, although male rats had higher SOD activity than females. Female rats had the highest CAT activities in the 4 Gy group, while male rats had the highest CAT activities in the 6 Gy group. CAT activities in the 8 Gy group were lower than those of the 2 Gy group for each gender and age. While MDA levels were decreased and CAT activities increased by GSH, SOD activities remained unchanged. The results indicate that gamma-ray radiation affects gender- and age-dependent MDA levels, SOD and CAT activities. Administration of GSH appears to be a useful approach to reduce radiation injury by reducing MDA levels and increasing CAT activities.