To study the genetic mutation, which could cause problems in spermatogenesis, we screened the point mutations of the FSH receptor gene (C566T) in idiopathic azoospermic men in Japan. We performed mutational analysis of the FSH receptor in 54 Japanese patients diagnosed for azoospermia with Sertoli cell-only (SCO) syndrome (n = 33), hypospermatogenesis (n = 11) and maturation arrest (n = 10). For mutation screening of the FSH receptor, polymerase chain reaction (PCR) amplification from genomic DNA with flanking intronic primers were used. On BsmI digestion, all patients demonstrated homozygous, normal exon 7 alleles with 51 and 27 bp fragments. The absence of any 78 bp fragments demonstrated that no heterozygous or homozygous mutant alleles were present in any patients. None of the 54 patients showed a C566T FSH receptor mutation. We could not confirm that the genomic mutation of the FSH receptor (C566T) is a common cause in Japanese azoospermic patients.