Previous studies have shown that activation of coagulation has an impact on the clinical course of lung cancer. This study was carried out to assess the potential prognostic significance of platelet count (P), prothrombin time (PT), partial thromboplastin time (PTT), anti-thrombin III (AT-III), fibrinogen (F), D-dimer (DD), factor II (F-II), factor VII (F-VII), factor X (F-X), protein C clotting (PCC), plasminogen (PL), and antiplasmin (AP) in 343 consecutive new lung cancer patients. A set of 32 anthropometric, clinical, physical, laboratory, radiological, and pathological variables was recorded prospectively for all patients. Patients were carefully followed-up, and their subsequent clinical course recorded. The most frequent abnormalities were of DD, F, and AT-III followed by F-VII, F-X, and F-II. Among the 12 clotting variables, the strongest relationships were those of F-II and F-X (Spearman rank (rs)=0.565), PT and F-VII (rs=0.562), F-VII and F-X (rs=0.514), PL and AP (rs=0.515), F and P (rs=0.490), AT-III and PCC (rs=0.476). Univariate analyses of survival showed that prolonged PT (p<0.043), and abnormally elevated DD (p<0.003), F (p<0.031), and P (p<0.047) were all associated with a poor prognosis. The multivariate model, however, did not confirm the prognostic significance of the coagulation factors. The results show subclinical activation of blood coagulation in lung cancer patients with early disease. In addition, clotting activation is confirmed as a predictor of survival, although not independently of other prognostic factors.