Nicotine is one of the main and toxic alkaloid in tobacoo which is largely absorbed in the body through cigarette smoking. A considerable amount of nicotine is found to be present in blood of tobacoo smokers and snuffers and is largely responsible for various physiological changes. Smokers are at a greater risk of various vascular diseases due to change in their hematological variables. It has been shown that administration of nicotine to healthy mice results in increase in white blood cell (WBC) and platelets (PLT) counts. High count of PLT may lead to thrombosis and other cardiovascular diseases. The levels of red blood cell (RBC) and haemoglobin (Hb) decreases with the dose of nicotine in mice. The levels of reproductive hormones (Lutenizing hormone & Testosterone) also decreases with the administartion of nicotine. So, high levels of nicotine in blood may affect fertility in men.