After venous occlusion (VO), D-dimer levels were measured by means of an ELISA technique, in citrated plasma clotted by thrombin and in serum from whole blood. D-dimer levels increased with duration of incubation (30 min to 24 hours). D-dimer values, both in clotted plasma and in serum (n = 12), incubated 4 hours at room temperature, correlated well with euglobulin clot lysis time (ECLT) (r = -0.85 and -0.89, respectively, p less than 0.002) and tissue plasminogen activator (t-PA) activity, (r = 0.82 and 0.83, respectively, p less than 0.002). D-dimer concentrations from plasma and serum (n = 25) were compared (r = 0.90, p less than 0.001). Healthy volunteers (n = 65) were tested to establish reference values in serum from post-occlusive whole blood samples incubated 4 hours prior to centrifugation. Finally, a patient group (n = 62) was examined. For the whole material (n = 152) such D-dimer concentrations correlated well with both ECLT (r = -0.85, p less than 0.001) and t-PA activity (r = 0.81, p less than 0.001). D-dimer levels in serum were determined by a latex agglutination test as well. These semi-quantitative values also correlated significantly with both ECLT (r = -0.86, p less than 0.001) and t-PA activity (r = 0.87, p less than 0.001). We conclude that measurement of D-dimer as described above, represents a simple and accurate method for assessment of global fibrinolytic activity following VO. The latex agglutination test is particularly suitable as a screening procedure.