The reliability of D-dimer (NycoCard D-dimer) and CRP (C-reactive protein) tests to exclude suspected deep venous thrombosis (DVT) and pulmonary embolism (PE) was investigated in 116 patients. Venography, ultrasonography or ventilation-perfusion lung scanning was used as the control method in 95, 5, and 14 patients, respectively, and pulmonary angiography in two patients, one of whom also underwent lung scanning, the other venography. Of the 116 patients, 52 had thromboembolism (46 DVT and 6 PE). The respective sensitivity, specificity, and negative and positive predictive values (NPV, PPV) were 94%, 27%, 85% and 51% for the D-dimer test, and 80%, 53% 76% and 60% for the CRP test. As venous thromboembolism is a life-threatening condition, the NPV of an exclusion test must lie very close to 100 per cent, and thus the study showed neither the D-dimer nor the CRP test to be a satisfactory exclusion test for use in cases of suspected DVT or PE.