The aim of this study was to establish the frequency of angiotensin-converting enzyme (ACE) insertion (I) or deletion (D) gene polymorphism in women with polycystic ovary syndrome (PCOS) and to examine the association of this polymorphism with insulin resistance. A total of 32 women with PCOS and 31 healthy, age- and body mass index-matched controls were studied. Serum lipids, fasting glucose, insulin and other hormones concentrations were measured. Homeostasis model assessment was used to estimate insulin resistance (HOMA-IR). DNA was extracted from peripheral blood leukocytes and genotyping of ACE I/D polymorphism was carried out by polymerase chain reaction. ACE genotypes were distributed as follows: DD was present in 16 (50%), ID in 12 (37.5%) and II in four (12.5%) PCOS patients, and DD in seven (22.6%), ID in 20 (64.5%) and II in four (12.9%) of healthy subjects. The frequency of D and I alleles were found in 69% and 31% of the PCOS group and 55% and 45% in the control group, respectively. There were no significant differences regarding the genotypic distribution and allelic frequency between the groups. However the ACE DD genotype was significantly associated with serum insulin concentrations and HOMA-IR measurement (both P = 0.005). ACE DD genotype is associated with an increased insulin resistance in women with PCOS. (C) 2010, Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.