The aim of the study was to assess the immunotoxic effect of dermally applied alpha-cypermethrin in rats based on phagocytic and bactericidal activity of neutrophils of peripheral blood, and the general toxic effect based on histological and ultrastructural examination of internal organs. The preparation was dermally applied in doses of 50 mg/kg and 250 mg/kg. It was administered to the tail skin of female Wistar rats, 4 hours daily for 28 days. After the experiment, the animals were anaesthetized and heart blood was taken in order to evaluate the activity of granulocyte system. The following organs were taken for histological examinations: brain, lung, heart, liver, spleen, kidneys, thymus and lymphatic nodes. Lung, liver, kidney and heart were used for ultrastructural studies. The results of the study showed that bactericidal and phagocytic activity of neutrophils was stimulated after administration of 50 mg/kg alpha-cypermethrin. Dermal application of the preparation resulted in slight histological changes in liver, kidney, lung and brain. Pathological changes in heart were observed only on the level of ultrastructure.