To determine the expression profiles of the DAZ gene family in men with and without spermatogenic failure.Prospective case study.University-based reproductive clinics and genetics laboratory.Thirty-four infertile men presenting with azoospermia.The mRNA transcript concentrations of the DAZ family genes (BOULE, DAZL, DAZ) and the housekeeping GAPDH gene in the testes of azoospermic men were examined by quantitative competitive-reverse transcription-polymerase chain reaction (QC-RT-PCR). The steady-state concentrations of mRNA encoding for each gene in each testicular sample were normalized by the amounts of GAPDH.Transcript ratios (gene/GAPDH) of BOULE, DAZL, and DAZ.The transcript ratios for BOULE, DAZL, and DAZ were significantly decreased in tissues with spermatogenic failure (hypospermatogenesis, maturation arrest, and Sertoli cell-only). However, the ratios of BOULE/DAZL and DAZ/DAZL did not reveal any significant difference in all tissues. Three patients with DAZ deletion possess lower transcripts of BOULE and DAZL.All members of the DAZ gene family play important roles in human spermatogenesis. Decreased concentrations of DAZ family members in men with spermatogenic failure may be due to the secondary effect of germ cell loss, and transcriptional control of BOULE, DAZL, and DAZ are not altered in the various degrees of spermatogenic failure. Although the sample size is limited, no compensatory increase of DAZL or BOULE transcription was found in men with DAZ deletion.