To investigate insulin receptor (INSR) genotype exon 17 frequencies in women with polycystic ovary syndrome (PCOS) and to elucidate its role in the pathogenesis of PCOS.The study involved 33 women with PCOS and 28 healthy control women who were genotyped for polymorphism of INSR gene exon 17 by single strand conformation polymorphism (SSCP) analysis. Body mass index (BMI), insulin sensitive index (ISI), the expression of INSR beta subunit, and serum concentration of luteinizing hormone (LH), total testosterone between the genotypes were compared.(1) The T-to-C mutation was observed in the INSR gene exon 17 (1008 bp). The frequency of the C/C genotype was significantly higher in patients (39%) than in the controls (11%) (P < 0.05). There was no significant difference in the distribution of genotypes between obese PCOS and non-obese PCOS, and between PCOS with insulin resistance (IR) and PCOS without IR. (2) In comparison of mutation genotype groups with wild genotype (T/T), ISI was significantly decreased (C/C genotype, P < 0.01; C/T genotype, P < 0.05), and no significant difference was observed in the other indices.There is polymorphism in INSR gene exon 17 in patients with PCOS. This variant leads to increased risk of IR in women with PCOS. It does not influence the expression of INSR beta subunit.