Energy-dispersive X-ray fluorescence (EDXRF) was used to determine the concentrations of Ca, Cl, Fe, Ni, P, K, Se, S, and Zn in heart, lung, liver, spleen, and kidney of adult albino rats 2 mo after they were subject to a single gamma gamma-radiation dose from 60Co at 5 gy. In female rats, K levels were significantly higher and the Ca levels significantly lower for the irradiated animals when compared to age-matched nonirradiated controls. Significant differences between irradiated and nonirradiated tissues were observed for other elements, although no sex-related differences could be found. Tissue damage and disturbances of biological functions were observed as a result of gamma-irradiation.