Kidney and thyroid functions interact with each other. Drugs used in treatment of any of them could have side reactions on any other organ. The effects of antithyroid medications on extrathyroidal organs could be due to oxidative stress and to damage in the renal cells. Aim: This work is designed to demonstrate the role of T4 in protection against the increase in oxidative stress caused by methimazole, and to detect if antithyroid drug-induced hypothyroidism (methimazole) or removal of thyroid by surgery causes damage of kidney cells or not. Methods:Twenty-five healthy adult male albino rats were used in the study. The animals were randomly separated into groups. Each group contained five rats: Group I (control group): This group received no drugs or treatment. Group II included rats with false thyroidectomy. Group III included thyroidectomized albino rats. Group IV included methimazole-induced hypothyroidism albino rats through receiving 60 mg/kg/day of methimazole in drinking water. Group V were administered methimazole (60 mg/kg/day) and l-thyroxine (T4) subcutaneous injection (20 μg/kg/day).The animals were anasethized and their abdomens were opened and both kidneys were removed, and immediately processed for histological & immunohistochemical study. Also oxidative enzymes were estimated. Rresults:Light microscopic examination of H&E stained sections showed marked damage of the structure of renal cortex in methimazole induced hypothyroidism group. This damage was concomitant with a decrease in kidney antioxidant enzymes. This damage was less pronounced in group of rats administrated T4 in association with methimazole. The cortex of kidney in rats of thyroidectomized group did not show any alterations in its micro structure.  Conclusion: Methimazole causes both of hypothyroidism and alteration of the kidney cortex. This alteration is not noticed in case of surgical thyroidectomy inducing hypothyroidism. L-Thyroxine (T4) could decrease the effect of methimazole on kidney cortex.