The aim of the study was to compare the information provided by both fasting and stimulated during a standard oral glucose tolerance test (oGTT) levels of glucose and insulin as regards glucose tolerance and insulin resistance in women with PCOS. Few criteria are used in practice to verify insulin resistance in PCOS--elevated fasting insulin, decreased basal glucose/insulin ratio (< 6 for glucose in mg/dl or < 0.333 for glucose in mmol/l), insulin increase of more than 100 lul during an oGTT, and HOMA index > 2. The study comprised of 94 women (mean age 21.8 +/- 5 = 8 ys, mean BMI-30.38 +/- 7 = 7 kg/m2), divided in 4 groups according to BMI--group with BMI < 25, n = 21; group with BMI25-30, n = 27; group with BMI = 30-35, n = 23 and group with BMI > 35, n = 23. An oGTT with parallel determination of blood glucose and insulin was performed in all patients. The ratio basal glucose/insulin and HOMA index were calculated. Glucose levels on the 2 md hour during the oGTT pointed at IGT (impaired glucose tolerance) and/or diabetes in 8.5% of the investigated patients while the fasting levels indicated disturbances in only 2.2% of them. Fasting insulin levels were in the normal range in a considerable part of PCOSE women, mainly those with normal weight, and were not predictive for the response of insulin to glucose load. Relative percent of patients with elevated fasting insulin rose with the increasing of BMI. Decreased glucose/insulin ratio, elevated HOMA index, and abnormal stimulation of insulin were seen in more than 2/3 of the PCOS women including nonobese ones. Information provided by the above three markers was similar and they could be used alternatively according to the particular case and assessment of the cost/benefit ratio.