Imazalil, cypermethrine and carbendazime are rezidually detected in food-stuffs in Republic Croatia. The aim of reasearch is to establish in which way of the number of leukocytes in pheripheral blood depend on the toxicological activity individual pesticide on the immune organs of Swiss mice exposed to them for the 28 days. It is supposed that number of leukocytes in blood will follow pathophysiological conditions in thymus, spleen and lymph node during pesticide treatment. Analysis of leukocytes showed the increase in total number of leukocytes in treatment with imazalil, carbendazime and combination of carbendazime. In all other groups percentage of granulocytes and agranulocytes was changed. The number of lymphocytes was reduced after combination of imazalile and carbendazime, and after imazalile, cypermethrine and carbendazime (used individually) was increased compared to control, especially in group imazalil. A similar thing happened with monocyte number, although the cypermethrine did not strongly increase the number of neutrophils. Probably these pesticides increased macrophage activity. The number of basophils was increased after treatment with all pesticides, especially after carbendazime. Eosinophils showed the similar effect. Cellularity and wight of immune organs was changed specifically to certain pesticide and their combinations and points to the dynamics of immunotoxicity tests. In groups where the cellularity and weigth of spleen, thymus and limph node decreased, it is possible that mobilization of new cells had been ocured in the blood leading to overall cellularity increase up to 28 days. In the organs in which cell number increased, cells are probably still in the phase of separation and not yet released into the blood. Sub-chronic low doses of these pesticides and their combinations are immunotoxic and immunostimulating except the combination of carbendazime and cypermethrine, which showed a strong cytotoxic potential and reduced the number of immunocompetent cells in the blood.