Many studies have demonstrated increased coagulation activation in cancer patients and have shown evidence of chronic, low-grade disseminated intravascular coagulation, although most patients remained asymptomatic. In general, patients have not been screened for deep venous thrombosis (DVT). We screened 98 patients with advanced malignancy for DVT using light reflection rheography. Coagulation profiles of DVT and non-DVT groups were studied. We found a high prevalence of DVT (50%) on screening. Overall, the patients had raised levels of fibrinogen (66% patients), factor VIII:C (43%), fragment 1 + 2 (71%) and TAT levels (89%). Patients with DVT had a significantly lower level of fibrinogen than those without (4.0 g/dl, SD 1.4, compared with 4.7 g/dl SD 1.6, P = 0.04). There was no significant difference in other coagulation or liver function tests between the DVT and non-DVT groups. The wide variation of results makes their interpretation difficult and unlikely to be of predictive value in estimating individual thrombotic risk.