We have previously shown that cancer patients with solid tumour disease have increased plasma levels of both the free and total forms of the coagulation inhibitor, tissue factor pathway inhibitor (TFPI), whereas patients with leukemia and related blood malignancies have levels within the normal range. We now report that also the median plasma levels of the Factor Xa (FXa)-TFPI complex were significantly higher in patients with solid tumours, compared to patients with haematological malignancy and healthy controls. There were significant positive correlations between the FXa-TFPI complex and total TFPI antigen (r=.47, P=.001) and TFPI activity (r=.33, P<.023). In plasma samples from patients with solid tumours, the ratio between the FXa-TFPI complex and free TFPI was 3.4 times higher than in patients with haematological malignancies. Increased levels of the FXa-TFPI complex in solid tumour disease may reflect both increased FXa generation and the increased TFPI concentration in the patients. It is speculated that high levels of the inhibitory FXa-TFPI complex in cancer patients may protect against microthrombosis and organ failure, which are relatively rare in cancer despite long-lasting hypercoagulation.