Aim: To complete comprehensive haplotype analysis of USP26 for both fertile and infertile men. Methods: Two hundred infertile men with severe oligospermia or non-obstructive azoospermia were subjected to sequence analysis for the entire coding sequences of the USP26 gene. Two hundred men with proven fertility were genotyped by primer extension methods. Allele/genotype frequencies, linkage disequilibrium (LD) characteristics and haplotypes of fertile men were compared with infertile men. Results: The allele frequencies of five single nucleotide polymor-phisms (370-371 insACA, 494T>C, 576G>A, ss6202791C>T, 1737G>A) were significantly higher in infertile patients than control subjects. The major haplotypes in infertile men were TACCGA (28% of the population), TGCCGA (15%), TACCAA (8%), TGCCAA (6%), TATCAA (5%) and CATCAA (5%). The major haplotypes for the control subjects were TACCGA (58% of the population), CACCGA (7%), CATCGA (6%) and TGCCGA (5%). Haplotypes TGCCGA, TATCAA, CATCAA, CATCGC, TACCAA and TGCCAA were over-transmitted in patients with spermato-genic defect, whereas haplotypes TACCGA, CACCGA, and CATCGA were under-transmitted in these patients.Conclusion: Some USP26 alleles and haplotypes are associated with spermatogenic defect in the Han nationality in Taiwan, China.