Androgens are essential for spermatogenesis. It has been postulated that androgen activity is modulated directly or indirectly by genetic variability in the androgen receptor gene sequence, including CAG/GGN polymorphisms and single-nucleotide polymorphisms (SNP). In this study, the frequency of 6 SNPs that constitute a haplotype in the androgen receptor sequence was determined by enzyme restriction assays and allele-specific polymerase chain reactions in 117 secretory azo/oligozoospermic men (93 idiopathic and 24 excryptorchidic), and in 121 controls with normal spermatogenesis (42 obstructive and 79 normozoospermic men) whose hormonal measurements and length of CAG/GGN polymorphisms were previously determined. The frequency of these 6 SNPs was not different between patients and controls. A total of 10 haplotypes (HAPs 1-10) formed by these 6 SNPs were found, and one of these haplotypes was observed with high frequency in the total population (HAP1, 83.2%; P < .001, χ(2) test). The frequency of the 10 haplotypes was not different between patients and controls, except for HAP5, which was only detected in one patient with a history of bilateral cryptorchidism (P = 0.014, Bonferroni test). On the other hand, no associations were found between the haplotypes studied and shorter or longer CAG or GGN polymorphisms. Interestingly, we found that the CAG 21 allele, which was previously correlated with an increased risk of idiopathic spermatogenic impairment, was more frequently found among the less common haplotypes that have higher follicle-stimulating hormone serum levels. In summary, we did not find an increased frequency of particular haplotypes in infertile men with idiopathic spermatogenic impairment compared with control men; however, we found that the CAG 21 allele, which appears to be associated with male infertility, is observed at a significantly higher proportion among the less common androgen receptor haplotypes.