Thromboembolic complications are common in patients with malignant disease. We studied the activation of coagulation in 106 patients with solid tumours and 72 healthy volunteers by measuring plasma levels of tissue factor, factor VIIa, factor XIIa, thrombin-antithrombin complex, and prothrombin fragments 1 + 2. Tissue factor was 67% higher in cancer patients (median 582 vs 349 pg/mL, p = 0.0006) and factor VIIa was 46% higher (100 vs 69 mU/mL, p = 0.0002), indicating extrinsic pathway activation. Modest activation of the intrinsic pathway (elevated factor XIIa) was seen only in patients with advanced disease or those receiving chemotherapy. Excess thrombin generation was manifested by elevations in thrombin-antithrombin complex and prothrombin fragments 1 + 2. Tissue factor pathway is clearly implicated in the hypercoagulable state of cancer.