Forty-two patients were prospectively evaluated with spiral volumetric computed tomography (CT) and selective pulmonary angiography of each lung to detect central pulmonary thromboembolism. Spiral volumetric CT images obtained with either 90 mL of 30% contrast material or 120 mL of 12% contrast material were graded as excellent or good in 98% of the examinations (41 patients). Diagnosis of pulmonary embolism with spiral volumetric CT was based on the direct visualization of intraluminal clots: partial filling defects (n = 41; 37%), complete filling defects (n = 51; 46%), "railway track" signs (n = 6; 5%), and mural defects (n = 14; 12%). All 23 patients with normal findings of spiral volumetric CT had normal findings of pulmonary angiography. With spiral volumetric CT, the finding of 112 central emboli (eight main, 28 lobar, and 76 segmental) corresponded exactly to the angiographic findings, but nine intersegmental lymph nodes were erroneously interpreted as filling defects. In one case of normal pulmonary angiographic findings, asymmetry in pulmonary arterial perfusion was misinterpreted as pulmonary embolism with spiral volumetric CT. Spiral volumetric CT can reliably depict thromboemboli in second- to fourth-division pulmonary vessels.