Title: Polymorphisms in post-insulin receptor signaling pathway in Saudi Women with Polycystic Ovary Syndrome: MSM Ardawi1 and AA Rouzi2, Departments of Clinical Biochemistry1 and Obstetrics & Gynecology2, Faculty of Medicine, King Abdulaziz University Hospital, King Abdulaziz University, Jeddah, Saudi Arabia. Objective: To determine whether post-insulin receptor signaling polymorphism (including PIK3R1, SLC2A4, SLC2A4RG and MEF2A genes) are associated with susceptibility to polycystic ovary syndrome (PCOS) or to insulin resistance (IR) of PCOS, Design: A prospective Case Control Study. Setting: Tertiary Referral University Hospital. Subjects: Two hundred Saudi women living in the Jeddah area were classified as follows: 100 with PCOS and 100 age-matched women without PCOS. Interventions: Blood samples were collected from all women with or without PCOS between 8:00-11:00, after an overnight fast. Main Outcome Measures: Frequency of PIK3RI, SLC2A4, SLC2A4RG and MEF2A polymorphisms in women with and without PCOS. Results: No significant differences were observed between the frequency of polymorphisms studied among Saudi women with and without PCOS. No single nucleotide polymorphism examined among the four genes studied was associated with the phenotype of PCOS. Conclusions: Polymorphisms in the PIK3R1, SLC2A4, SLC2ARG and MEF2A genes are not associated with PCOS phenotypes in Saudi women. 1