We quantitated urokinase and tissue plasminogen activator (u-PA, t-PA), plasminogen activator inhibitor 1 and 2 (PAI-1, PAI-2), and fibrinolytic activity in peripheral blood (PB), tumour blood (TB), peritoneal/ascitic fluid (PAF) and cystic fluid (CF) from 104 patients with benign and 36 patients with malignant ovarian tumours, and in peripheral blood from 62 healthy controls. PB levels of u-PA were higher in patients with benign and malignant tumours than in controls. High concentrations of u-PA were found in CF, but not in TB, suggesting that u-PA is released by the tumour tissue, but not by the tumour vasculature. PB levels of t-PA were higher in both tumour groups than in controls. Increased levels of t-PA were found in TB, but not in CF, indicating that t-PA is released by the tumour vasculature, but not by the tumour tissue. PB levels of PAI-1 were higher in patients with both benign and malignant tumours than in controls. High levels of PAI-1 were present in both TB and CF from malignant tumours, suggesting that PAI-1 is released from the tumour vasculature as well as the tumour tissue. Elevated concentrations of PAI-2 were found in CF, but not in TB, indicating release from the tumour tissue, but not from the vasculature. High levels of t-PA, PAI-1 and PAI-2 were found in PAF of malignant tumours, and resorption from this compartment may explain elevated PB levels in patients with ascites. None of the PAs/PAIs proved useful as a PB marker for detection of early stage ovarian cancer. However, an index based on PAF levels of t-PA and PAI-1 discriminated between malignant and benign ovarian cysts in the absence of ascites. In addition, our study stresses the importance of including patients with benign tumours as well as healthy controls when markers for malignant tumours are evaluated.