Pentoxifylline is a haemorrheologic agent often used in the treatment of peripheral vascular disorders. In this study, we measured sperm motility with a trans-membrane migration method and investigated the effect of this drug in the treatment of male infertility. We found that pentoxifylline increased motility of ejaculated spermatozoa in vitro from both normal and asthenozoospermic samples. After giving pentoxifylline to patients with asthenozoospermia for 3 months, sperm motility significantly increased, but sperm concentration did not increase. From the above results, it can be concluded that pentoxifylline is a useful drug in the treatment of normogonadotropic asthenozoospermia.