[The present and the future of treatment of male infertility]. 
About 90% of male infertile patients are complaint of semen with poor quality, and of which majority are caused by idiopathic disturbance of spermatogenesis.  To date, various trials have been made to stimulate spermatogenesis by means of pharmaceutical administrations, their efficacies were, however, poor as expected.  The treatment of the patients with poor quality semen is, therefore, mainly focused on artificial insemination, such as intrauterine insemination (IUI) and in vitro fertilization-embryo transfer (IVF-ET), etc. ( 1) To inseminate the sperm artificially, it is necessary to separate progressively motile sperm with normal morphology from seminal plasma, immotile and abnormal sperm, leucocytes and bacteria.  There are two methods for separating progressively motile sperm, one is the density gradient centrifugation and another is the diffusion by their own motility.  We have developed various types of density gradients using Percoll, a modified silica gel; the mono-layer Percoll method and the cushion method are employed for sperm concentration, and the discontinuous Percoll density gradient with 4 steps and the continuous-step density gradient are capable of separating progressively motile sperm.  The continuous-step density gradient have been employed for 271 cases of IUI, and successful 84 pregnancies were obtained with the pregnancy rate of 30.9%. ( 2) Cryopreservation of sperm produce various advantages in the treatment of male infertility.  Cryoaccumulation of oligozoospermic semen is effective for obtaining a sufficient number of sperm, and frequent insemination with cryopreserved sperm increase the chance of fertilization.  To improve the quality of cryopreserved sperm, ejaculated semen was concentrated prior freezing by means of the continuous-step density gradient.(ABSTRACT TRUNCATED AT 250 WORDS)