This study aimed to evaluate plasminogen activator inhibitor-1 (PAI-1) activity in PCOS. Thirty women with PCOS - 15 normal-weight and 15 obese - and 30 healthy women matched as a group for age and body mass index (BMI) were recruited. The homeostasis model assessment (HOMA) score was significantly elevated in obese compared with normal-weight women, in both PCOS women and controls. HOMA score was significantly higher in both PCOS groups relative to controls. After further adjustment for BMI, PAI-1 activity (IU/ml +/- SD) was significantly higher in the PCOS groups compared with controls. A significant positive correlation was found between HOMA score and BMI in PCOS and control groups. Serum PAI-1 activity was significantly related to BMI and HOMA score. When considering two BMI subgroups, there was no significant difference in the relationship between serum PAI-1 activity and HOMA score in both the control and PCOS groups. No other significant relationship was found between serum PAI-1 activity and any other hormonal or metabolic parameter. In conclusion, women with PCOS have significantly elevated PAI-1 activity independent of obesity, and it is speculated that elevated PAI-1 activity may be a factor in the increased cardiovascular morbidity seen in PCOS.