Objective: There is lots of oxygen reaction element in cigarette smoking that induce reactive oxygen stress (ROS) in the body ROS can make DNA damage in somatic and germ cells. The purpose of this study was to evaluate the effect of smoking on sperm DNA integrity in infertile patients by comet assay. Materials and Methods: DNA damage in sperm of 72 men undergoing IVF and ICSI treatment was measured by comet assay and DNA damage was compared between smoker and nonsmoker groups by t-test using SPSS 11.5 software. Results: The result show that significant different between sperm DNA integrity among smoker and non smoker groups (p=0.05). Conclusion: it can be concluded that the cigarette prone sperm DNA damage.