We investigated 128 patients with suspected deep vein thrombosis and 26 patients with suspected pulmonary embolism. Plasma cross-linked fibrin degradation products were measured instantly by a new rapid and fully quantitative immunoturbidimetric assay (Boehringer Mannheim) which recognizes the D-dimer epitope by antibody-coated latex particles. Diagnosis of deep vein thrombosis was established by either ascending venography (n = 105) or colour duplex ultrasound (n = 8), whereas for the exclusion of deep vein thrombosis only venography was accepted. The sensitivity/specificity for the diagnosis of deep vein thrombosis was 98%/44%. Patients with suspected pulmonary embolism were examined by pulmonary angiography (n = 19) or perfusion lung scanning alone (n = 6), if sufficient. One pulmonary embolism was diagnosed at post-mortem examination. For pulmonary embolism, sensitivity/specificity was 100%/50%. These findings indicate that the new immunoturbidimetric technique is as reliable as former ELISA methods and allows to rule out thromboembolic disorders. D-dimers showed a correlation to the extent of the deep vein thrombosis, proximal thrombosis producing higher D-dimer levels. Patients presenting immediately after the onset of symptoms were found to have higher D-dimers than patients examined after a few days. A quantitative D-dimer measurement thus seems to provide precious additional information of the duration and the extent of thromboembolic disease.