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Background&Objective: The infertility and its psycological problems can be considered as one of the important difficulties among married couple. Nearlly half of the infertility related to the men. This study was set up to determine the most common risk factors of male infertility in men attending infertility clinics in Shiraz. Materials&Methods: A case – control study was conducted in which 268 men. 161 fertile men were compared with 108 infertile men from the point of risk factors such as smoking habits, drug consumption, hernia, varicocele, job and BMI. Results: Logestic regression analysis, Risk estimate (adds Ratio), and t-test demonstrated that hernia, varicocele, ranitidine consumption, Job and BMI all have statistically significant associations with infertility in men. Odds Ratios of 2.5 for hernia, 4 for varicocele, 2.9 for ranitidine consumption, 2.3 for workers (simple, semiskilled and skilled), t=3.5 (P<0.05). With an increase of one cigarette per day there was decrease 1% in motility of sperm .With an increase of one year of cigarette smoking, the number of sperm was decrease about 800000. The BMI in infertility men was <25. Conclusion: This study showed that the most common factor in men infertility in Shiraz are varicocele and hernia and hard works can cause testicular injury.