The histological structure of rabbit spleen after bendiocarb administration was studied. Bendiocarb was perorally administered for 30 days. At day 10, 20 and 30 morphometric analysis was realized. Quantitative evaluation showed that in the control group the relative spleen volume of white pulp ranged from 35.03 ± 10.94 % and the relative volume of red pulp 64.97 ± 10.94 %. In all experimental groups were detected significantly higher relative volume of red pulp and the lower relative volume of white pulp, except on day 30. The experimental groups showed a significant increase in the number of lymphocytes in comparison with the control group. On day 10 we observed a significant increase in diameter of investigated lymphocytes. The results of our study determined structural alterations in spleen structure after bendiocarb administration, which probably causes alteration in the immune system.