Molecular and cytogenetic parameters were estimated in male CBA/lac mice exposed to chronic low dose-rate gamma-radiation (62 cGy/year) for 40, 80, 120, 210, and 365 days. After 40 days of exposure (6.7 cGy), spleen lymphocyte susceptibility to hydrogen peroxide was shown to increase. However, beginning from the day 120 of the treatment (20.4 cGy), the opposite effect was observed. An increase in number of the DNA-protein crosslinks was recorded in spleen lymphocytes only on day 40 of the experiment. The number of DNA breaks increased significantly beginning from day 120 of the experiment, as shown by the DNA-comet method. On the day 210 of irradiation, the frequency of abnormal sperm heads in the mice significantly increased. The number of normochromatic micronucleated erythrocytes of the peripheral blood remained unchanged.