The polycystic ovary syndrome (PCOS) is one of the most common abnormalities in women of reproductive age. Many researchers found evidence that a susceptibility gene for PCOS is located on chromosome 19p13.3 in the insulin receptor (INSR) gene region. We investigated the association between the polymorphisms of the INSR gene on phenotype, metabolic parameters, reproductive hormones and anthropometric measurements of 90 young Saudi Females with PCOS and 122 healthy women (controls) aged 19 to 36 years. The subjects were divided into 6 groups according to their body mass index BMI; lean (BMI 18-24), overweight (BMI 25-29) and obese (BMI ≥30). RESULTS: BMI, WHR, LH, T, E2, insulin, cholesterol, Triglyceride and LDL of PCOS group were higher than those of control group. C/T single nucleotide polymorphism frequency at exon 17 of INSR in patients with PCOS was significantly higher than that in normal female (31% vs. 17%, P < 0.0005). The frequency of the T allele was significantly increased in lean patients with PCOS compared with lean controls, 37.50% of lean patients with PCOS but only 10.83% of lean controls had the C-to-T substitution (relative risk, 4.5; P<.0001). In contrast, the frequency of the T alleles did not differ significantly between obese patients with PCOS (29.00%) and obese controls (22.22%, P=0.29). Interestingly, logistic regression analysis reveled strong association between C\T polymorphism of INSR gene and increased levels of LH (P< 0.001). In conclusion, the 1058 site nucleotide polymorphism of insulin receptor gene is one of the susceptibility genes in patients with PCOS, especially in non-obese PCOS patients.