Male rats of the Wistar strain were continuously irradiated with an exposure of 0.57 Gy (60 R) of gamma-rays from a 60Co source. Irradiation lasted from 1 to 50 days in an experimental field, in which control animals shielded from radiation were also placed. After a 16-h starvation, concentration of glucose in the blood and of glycogen in the liver and heart was determined 1, 3, 7, 14, 21, 25, 32, 39 and 50 days after the beginning of irradiation. Concentration of blood glucose in irradiated rats did not practically differ from that of control animals during the whole period of investigation. Concentration of liver glycogen in irradiated animals was higher than that of the controls during all time intervals, except for day 1. Values of glycogen in the heart muscle were approximately identical in irradiated and control rats, except for day 21, on which they sharply increased in the irradiated animals. In addition to the investigation of blood glucose and tissue glycogen during continuous irradiation, we followed these parameters immediately, and 1, 6 and 12 months after continuous irradiation with a daily exposure of 0.57 Gy (60 R) up to a total exposure of 14.35 Gy (1 500 R) of gamma-rays. Considerably higher values of liver glycogen were detected in irradiated rats immediately and 1 and 6 months after the end of irradiation.