There is no clear clinical evidence that smoking is harmful to male fertility. Smoking may lead to an increased incidence of high blood pressure, high cholesterol and coronary heart disease, and the nicotine and carbon monoxide in cigarette smoke may lead to the development of atherosclerosis. This in turn further affects spermatogenesis. Smoking may lead to a decrease in the normal sperm count, and in patients with severe smoking, it may also lead to malformation of the sperm. The longer the patient smokes, the normal sperm count and sperm motility may be reduced. The main component of tobacco has nicotine, which when burned, generates a large number of toxic chemicals, radioactive substances and carcinogens, and poses a threat to health. Patients are advised to actively quit smoking.