The aim of this study was to determine if the absence of circulating D-dimers, as determined by latex agglutination assays, can correctly exclude the presence of pulmonary embolism using pulmonary angiography as the diagnostic endpoint. Blood samples were obtained prospectively at the time of angiography for suspicion of acute pulmonary embolism. Plasma was assayed for D-dimer by five different latex agglutination assays. Angiographic evidence of pulmonary emboli was found in 34% (35/ 103) of patients. The latex agglutination assays had sensitivities of 97 to 100% and specificities of 19 to 29%. The negative predictive value was 94 to 100%. However, a negative D-dimer was rare in patients with recent surgery, malignancy, or total bilirubin > 34 micromol/L (> 2 mg/dl). In 31 patients suspected of pulmonary emboli but without these confounding factors, the five D-dimer assays were negative in 46 to 55% of patients with normal pulmonary angiograms. The negative predictive value in these patients was 100% by all five latex agglutination assays tested. The latex agglutination assays for D-dimer, when the pulmonary angiogram is used as the diagnostic endpoint and in the absence of recent surgery, malignancy, or liver disease, appears to be a clinically useful test in the diagnosis of acute pulmonary embolism.