[en] The level of DNA-protein cross-links (DPC) in mouse thymocytes and spleen lymphocytes, the number of abnormal sperm heads (ASH) and the number of micronuclei (MN) in normochromatic erythrocytes (NCE) of peripheral blood were studied in mice exposed to long-term low-intensity gamma radiation (0.072 cGy/day) and lead with drinking water (0,3 mg Pb²⁺/l) for 20, 40 and 80 days. The results of the studies have demonstrated that the dependence of the DPC level on the total dose (exposure time) of gamma-radiation and/or lead is nonlinear. The maximal level of DPCs in cells of the lymphoid organs upon exposure to gamma-radiation or lead was recorded on the 40-th day of the experiment. On the 80-th day of the experiment the DPC level in cells of each of the organs returns to the control values. It is probable that the nonmonotonous pattern of the dose-effect curves may reflect the activation of the compensation-restoration processes in order to preserve homeostasis in response to the damaging action. Special notice should be made of a similar character of changes in the DPC level upon exposure to heavy metals and radiation. This fact suggests the nonspecific character of the mechanisms of DPC formation at low intensities (doses) of these genotoxic agents. This conclusion is also confirmed by the similarity of the curves characterizing the DPC level for thymocytes and splenocytes. The combined exposure to gamma-radiation and lead did not induce a significant increase of the DPC level. The long-term exposure to gamma-radiation or the combined exposure to gamma-radiation and lead caused an increase in the ASH frequency. No increase was found in the frequencies of MNs in NCEs and reciprocal translocations in spermatocytes. Summing up the results obtained it can be concluded that the action of gamma-radiation and lead at the applied doses induces an increase in the DPC level in thymocytes and splenocytes with in the first 40 days of exposure and an increase in the ASH frequency on the 80-th day, but these changes do not result in pronounced cytogenetic effects. (author)