OBJECTIVE(S) : To find out the correlation between the mathematical indices of insulin resistance (IR) and body mass index (BMI) in polycystic ovarian syndrome (PCOS). METHOD(S) : Sixty-six PCOS women were studied. BMI was calculated in each case and the mathematical indices of insulin resistance namely, fasting glucose: fasting insulin ratio (G: I), homeostatic model assessment (HOMA), and quantitative insulin sensitivity check index (QUICKI) were calculated from the values of fasting sugar and fasting insulin level. Patients were classified into three groups depending on BMI - Group A (<= 24 kg/m(2), n=22), Group B (25-29 kg/m(2), n=22), and Group C (>= 30 kg/m(2); n=22). Intra-group and inter-group correlation coefficients were calculated between these parameters. RESULTS : Strong negative correlations between G: I and HOMA and strong positive correlations between G: I and QUICKI were found in each of the three groups. HOMA and QUICKI showed strong negative correlations in each of the three groups. There were moderate positive correlations between the respective indices among Group A and B. None of the indices showed any significant correlations with BMI, both intra-group and inter-group. CONCLUSION(S) : Mathematical indices of insulin resistance have mild correlations with BMI in PCOS, in contrast to many other insulin resistant states and should be utilised cautiously in routine clinical practice in the management of PCOS.