Polycystic ovary syndrome (PCOS) is a common endocrinopathy which is characterized by ovarian androgen excess. PCOS has a strong genetic component but the pathogenetic mechanisms responsible for hyperandrogenemia are still unknown. The CYP11A1 encodes the cholesterol side-chain cleavage enzyme that catalyzes the first and rate-limiting step of steroidogenesis. A promoter polymorphism (TTTTA)n CYP11A1 has been reported to be related to the risk of PCOS but the results were controversial.We determined this polymorphism in a cohort of 256 PCOS and 109 healthy control women. Using two models (dominant model for allele with 4 repeats and dominant model for long alleles, i.e. 7 and more repeats) we did not find either the difference in allele and genotype distribution between PCOS and controls or the influence of polymorphism on serum testosterone and androstendione levels. However, the PCOS carriers of long alleles had lower FSH, total- and LDL-cholesterol compared to the carriers of short alleles (p = 0.007; p = 0.02; p = 0.02, ANOVA). In controls, the non-carriers of allele with 4 repeats had significantly higher DHEA-S (p = 0.02, ANOVA) levels than the carriers of allele with 4 repeats.Despite of some associations found, it seems that the promoter variability of CYP11A1 does not play a key role in the pathogenesis of PCOS.