In this prospective study different semen parameters of fertile smokers were compared with fertile non-smokers. 58 men with proven fertility (17 smokers and 41 non-smokers) at the same age were evaluated. Smokers had significantly less spermatozoa with motility grade A (p<0.01), B (p<0.05), and C (p<0.05), and more abnormal forms in the ejaculate (p< 0.001). The percentage of sperm with head defects (p<0.05) and cytoplasmic droplets (p<0.001) were also significantly higher in smokers. No differences were found in the assessment of semen volume, total sperm count, hypoosmotic swelling test, induced acrosomal reaction and acidic aniline blue staining test between two groups (p>0.05). However the concentration of leukocytes in semen was significantly higher in smokers (p<0.001), which can suggests oxidative imbalance in the ejaculates of these men. Our data demonstrate that cigarette smoking is associated with reduced semen quality which could worsen fertilizing potential in fertile men.