Objective of this study was to investigate changes in biological activity of blood leukocytes in Japanese quails, caused by zinc and cadmium administration. Four groups of Japanese quails were used. Three experimental groups of quails were exposed either to Cd (0.12 mg Cd/quail), Zn (4 mg Zn/quail) or a combination of Cd and Zn (0.12 mg Cd, 4 mg Zn/quail), which were added daily to the drinking water. The fourth group was the control group. The metabolic activity of phagocytes and mitogenic activation of lymphocytes to phytohemaglutinine (PHA) were determined on day 37, 58 and 118 of exposure. The numbers of peripheral blood leukocytes of Japanese quail after cadmium and zinc addition in all groups of birds were without significant differences, however, the functional activities of phagocytes and lymphocytes in the Cd-group of quails were significantly decreased. The metabolic activity of phagocytes decreased significantly at all time points analysed (P < 0.05-0.001) in comparison to the control group and the Cd-Zn group. Similarly, the response of lymphocytes to PHA activation in the Cd exposed group of quails decreased significantly on day 58 and 118 of exposure when compared to the control group (P < 0.05) and Zn-group of quails (P < 0.01). Zn in combination with Cd eliminated the immunotoxic effect of Cd on metabolic activity of phagocytes and improved lymphocyte answer to PHA, when compared to the Cd-group on day 58 and 118 of metal administration. The results of the present study indicate that cadmium caused a significant decrease of metabolic activity of phagocytes and mitogenic activation of lymphocytes in peripheral blood of Japanese quails. Simultaneous administration of Zn and Cd eliminated the immunotoxic effect of Cd on functional activity of phagocytes and lymphocytes, and zinc improved both investigated functional parameters of immune cells.