Purpose of investigation: Approximately 15% of couples are infertile, and male and female factors are believed to be equally important. Genetic mechanisms are implicated in aspects of male infertility and male mice lacking the gene Etv5 exhibited azoospermia with loss of germ cells: a phenotype identical to human Sertoli cell-only syndrome (SCOS). The ETV5 gene family encodes transcription factors sharing the evolutionarily conserved DNA-binding ETS domain. Therefore, the authors hypothesized that ETV5 variants might be associated with azoospermia caused by SCOS. Materials and Methods: ETV5 was sequenced in 140 Japanese men with SCOS and in 116 healthy controls using the Sanger method. Results: Four single-nucleotide polymorphism variants (SNPs 1-4) were detected in the patient group. An association study was performed for patients and controls. Two ETV5 variants, SNP2 and SNP3, were nominally associated with susceptibility to SCOS (p = 0.002 and p < 0.001, respectively). Conclusion: These results indicate a potential role for ETV5 in human spermatogenesis.