BACKGROUNDThe activation of the clotting‐fibrinolytic system in cancer patients is common and represents an unfavorable clinical sign. D‐dimer (DD) is a sensitive marker of fibrinolysis.METHODSThe current study comprised 826 new lung carcinoma patients seen consecutively in a single institution over a 10‐year period (1992–2001). For each patient, 31 variables, including DD and survival duration, were available for analysis.RESULTSOnly weak relationships between DD and the other variables were found. The DD variable correlated best with the level of lactate dehydrogenase, performance status, tissue polypeptide antigen, stage of disease, and the number of metastases (rho = 0.33, −0.25, 0.18, 0.18, and 0.15, respectively). The D‐dimer distinguished patients with different prognoses. The median survival periods were 154 days (95% confidence interval [CI], 122–189 days) and 308 days (95% CI, 227–409 days; log rank statistic, 26.56; P < 0.01), respectively, for abnormally elevated and normal values. The difference was greater in patients with adenocarcinoma and in patients presenting with a less advanced disease, especially in patients with pathologic Stage Ia disease. The best multivariate survival model selected 10 significant covariates, including DD.CONCLUSIONSThe authors recommend measuring the plasma level of DD in all new lung carcinoma patients. This measurement may help to formulate individual prognoses and can be used to indicate adjuvant treatment for surgical patients. Cancer 2003;97:3044–52. © 2003 American Cancer Society.DOI 10.1002/cncr.11432