Toxicity of dermally absorbed dichlorvos was studied in rats, based on its effects on internal organs, and on phagocytic and bactericidal activity of the neutrophile system. The studies were conducted on 30 female rats of Wistar strain. The animals were divided into three groups, two of which were experimentally exposed to dermal absorption of dichlorvos (37.5 mg/kg - 1/2 LD50; or 7.5 mg/kg - 1/10 LD50;), and one control group which was exposed to dermal absorption of the solvent. The animals were exposed to dermal absorption for 4 hours daily for a period of 4 weeks. After 28 days, the rats were anaesthetized, blood was drawn from the heart to evaluate the activity of the neutrophilic system, and the internal organs excised for histological and ultrastructural studies. Dermally absorbed dichlorvos caused histopathological changes in lungs, lymphatic glands and thymus, as well as histopathological and ultrastructural changes in liver, kidneys and heart muscle. Dichlorvos stimulated the bactericidal and phagocytic activity of neutrophils.