The aim of the study was to prospectively investigate the efficacy of recombinant human follicle-stimulating hormone (rhFSH) in the treatment of various types of male-factor infertility at a single university hospital. The study included 61 infertile men receiving rhFSH because of various type of male infertility. Treatment included 100-150 IU of rhFSH 2-3 times/wk. All men were divided into 4 groups: hypogonadotropic hypogonadism (n = 21), isolated follicle-stimulating hormone (FSH) deficiency (n = 13), idiopathic oligoasthenospermia (n = 16) and maturation arrest on testicular biopsy (n = 11). Total motile sperm count (TMSC), serum FSH level, and testicular volume were compared before and after treatment in all groups. In the hypogonadotropic hypogonadism group, spermatozoa appeared in the ejaculate, with a mean TMSC of 6.67 +/- 1.57 million, in 15 of 21 patients (71.4%) who were totally azoospermic before the treatment. In the isolated FSH deficiency group, TMSC significantly increased from 6.64 +/- 3.27 to 32.4 +/- 9.09 million after the treatment (P = .003). TMSC did not significantly increase in the idiopathic oligoasthenospermia group. Two of the men with maturation arrest (18.1%) had spermatozoa in the ejaculate after the treatment. rhFSH therapy may be effectively used to improve sperm parameters in infertile men with hypogonadotropic hypogonadism and isolated FSH deficiency. In addition, rhFSH may effect some improvement by either providing sperm in ejaculate or increasing intracytoplasmic sperm injection success in infertile men with maturation arrest.