Background: PCOS is associated with insulin resistance and premature coronary artery disease (CAD). Hyperhomocysteinaemia is a risk factor of atheroclesrosis. Objectives: To compare plasma homocysteine in women with PCOS and matched controls and to correlate plasma homocysteine with fasting insulin concentration Method: Case control study of Sri Lankans (SL), British Asians (BA) and Caucasian (C) with and without PCOS: SL (80 vs. 45), BA (47 vs. 11) and C (40 vs. 22). Fasting homocysteine (Fluorescence Polarization Immunoassay, IMX System) was analysed and correlated with age, body mass index (BMI), central obesity and fasting insulin. Results: Mean plasma homocysteine (Hc) was significantly higher in all PCOS groups (SL 9.25 vs. 8.26, p= 0.03; BA 7.73 vs. 5.29, p< 0.0001; C 8.81 vs. 6.34, P= 0.007) while SL PCOS had significantly greater Hc (p= 0.0012) than other PCOS groups. Asian …