Introduction: Idiopathic infertility is the most common cause of infertility among the males who are usually treated empirically. Two new drugs used in empirical therapy are: Pentoxifylline and L- Carnitine. However, there is no comparison study about their effects. This study aims at comparing the therapeutic effects of Pentoxifylline and L- Carnitine in infertile male patients with Idiopathic Materials and Methods: This clinical trial study was performed on 38 patients with Idiopathic Asthenospermia during the years of 1385-86 in Mashhad, Iran. In addition to filling out the questionnaire based on demographic data, Spermogram test and analysis were administered during a three- month period.Results: Nineteen male patients were treated with L-Carnitine in 3 months. In 5 cases, the wives (26.3%) got pregnant, but no significant difference was observed the spermogram parameters of the male subjects. On the other hand, in the group treated with Pentoxifylline, the wives of 10 subjects (52.6%) got pregnant and the analysis of the males’ spermograms after the medical therapy revealed significant difference in density parameters as follows: Motility (P=0.011); Spermotility (P=0.0001); Motility Index (P=0.0001).Conclusion: Pentoxifylline showed more promising results for the treatment of male idiopathic infertility.