Isobutyl-2 cyanoacrylate (IBC) was used to embolize the bronchial arteries of 14 patients with severe hemoptysis. The site of bleeding was supplied by a bronchial artery from the aorta in 11 cases and from a right bronchointercostal trunk in three. IBC was injected after previous reduction of the blood flow in the artery by embolization with particles of dura mater. In all cases, bleeding stopped immediately after occlusion and no spinal cord complications were observed. The results indicate that IBC may be a valuable occluding agent in severe hemoptysis, since it produced virtually permanent occlusion of both the distal and proximal parts of the artery. In 13 patients, bleeding did not recur throughout follow-up periods of 2-17 months. In one patient, it recurred 12 months after embolization but stopped after occlusion of another bronchial artery with IBC. It should be noted, however, that immediately after embolization, five patients experienced violent transient retrosternal burning, and one patient experienced dysphagia and fever for 2 days. Since mediastinal ischemia cannot always be avoided, this procedure must be reserved for cases of severe hemoptysis for which surgical treatment is contraindicated.