The diagnosis of pulmonary embolism remains a difficult issue. In a previous study of patients submitted to ventilation--perfusion (V-P) scintigraphy we suggested that measurement of D-dimer might be of value for ruling out the diagnosis of pulmonary embolism if the plasma level was less than 500 micrograms/l (ELISA). In the present paper, this cut-off was validated in a consecutive series of 21 patients who were submitted to pulmonary angiography. Sensitivity and specificity were 100% and 36%, respectively. When these data were pooled with the results obtained following V-P scintigraphy (total number of patients = 67), sensitivity, specificity, and positive and negative predictive values were 100%, 70%, 59% and 100%, respectively. It is therefore worthwhile to further evaluate the value of the plasma measurement of D-dimers, especially in patients with inconclusive lung scintigraphy.