This study evaluated dimethylhydrazines' carcinogenic and toxic effect (DMH) in male rats; 30 albino rats were divided into three groups, randomly ten rates for each one. Group 1 control group was lifted for water only, group 2 was treated with DMH at a dose of 10 mg /kg bw in 0.9% sodium chloride subcutaneously once weekly for eight weeks, and group 3 was treated with DMH at a dose of 20 mg /kg bw in 0.9% NaCl subcutaneously once weekly for eight weeks. Liver grossly congested with pinpoint hemorrhage in a dose of 10 mg/kg of bw and enlarged in a dose of 20 mg/kg bw. Congestion of blood vessels in the heart with hypertrophy of myocardium in a dose of 20 mg/kg bw. Kidney grossly appears normal in both doses. Lesions of the liver treated with DMH in the dose 10 mg/kg BW show discontinuation of hepatocytes, infiltrations of inflammatory cells, and vacuolar degeneration of hepatocytes with apoptotic bodies. Section of the liver treated with DMH in the dose 20 mg/kg BW shows acute hemorrhage and focal necrosis of hepatocytes with edema. Heart treated with DMH in a dose of 10 mg/kg BW shows discontinuation of myocardial muscle fibers and infiltrations of inflammatory cells. In contrast, lesions in the dose 20 mg/kg bw show foci of inflammatory cells with cardiomyopathies of myocardium and congestion of blood vessels. Kidney treated with DMH in a dose of 10 mg/kg BW shows degeneration of epithelial cells lining renal tubule, infiltrations of inflammatory cells, hyaline cast with atrophy of glomerular tuft, increased space of Bauman's, and cloudy swelling. The kidney section treated with DMH in a dose of 20 mg/kg bw shows hemorrhage between renal tubules, congestion of blood vessels, infiltrations of inflammatory cells, a renal cyst, and degeneration of glomeruli.