The hemato-cytogenetic and endocrine toxic effects of mancozeb (technical and formulated) have been studied in male Wistar rats. Sublethal doses administered orally for 28 day resulted in several alterations. Notable significant changes in organ weight ratio were recorded where the technical showed decreasing pattern, while the formulated showed increasing trend indicating alteraion of the physiological state of the exposed animals either in the whole body weight or in the function of internal organs. In the hemato-toxicologic context, blood indices were affected by exposure where technical compound exhibited increasing pattern of red and white blood cells while the formulated caused decreasing in red blood cells although the erythrocytes indices showed significant elevation after all dose regimens. Furthermore, technical mancozeb at 500 mg/kg resulted in slight significant increase (p < 0.01) in the frequency of micronuclei in the polychromatic erythrocytes of bone marrow (10±0.816), while the same dose of the formulated induced a highly significant increase (p < 0.001) in the frequency of micronuclei (14±0.816) when compared with the negative control raising concern for its mutagenic potential.   Additionally, ultrastructural changes of the thyroid gland were recorded after exposure to both forms of the compound. It may be suggested that hormonal imbalance is the causative factor related to the thyroid follicular hyperplasia. In a conclusion mancozeb; particularly the formulated form, is suggested to be of toxicological concern due to a potential hazard posed to the effect on thyroid gland and its genotoxic effects. Further studies should delineate the respective pathways of mancozeb intoxication.