Pulmonary emboli were produced in 15 dogs and studied with serial angiography. The most common angiographic sign in the embolized animal was a filling defect and/or a cut-off, with or without regional delay in arterial flow. Less common findings were regional hypovascularity, slow arterial washout with capillary staining, tapered arteries, and beading of small vessels.Two hundred patients were studied with pulmonary angiography for the possible diagnosis of pulmonary emboli. On the basis of pathologic proof in 28 cases (13 with emboli and 15 without pulmonary emboli), criteria were established for the angiographic diagnosis of pulmonary emboli. The most important finding was a filling defect and/or cut-off, with and without regional delay in arterial flow. In 58 patients with these angiographic findings who survived, a high incidence of the clinical findings of pulmonary emboli was found.Less significant pulmonary angiographic findings noted in the dog were found to be associated with many unrelated cardi...