Following embolization of the superior mesenteric artery with autologous blood clots, local catheter thrombolysis using streptokinase was performed in 14 pigs. In 7 animals the abdomen was kept closed during the time of obstruction (3 h) and subsequent lysis (up to 3 h) until angiography revealed patent vessels. Macroscopic and histologic examination showed small bowel distension and severe mucosal damage in all animals. In a second series of 7 pigs, lysis was performed after 1 2 and 3 h of ischemia. Angiographic and histologic findings were compared with surface oxygen tension and myoelectrical activity. Bowel wall anoxia and disappearance of slow waves were reversible after up to 4 h of ischemia (2 h occlusion, 1–2 h lysis). Persistent anoxia and irreversible disappearance of slow waves in combination with severe mucosal damage were suggestive of pregangrenous alterations of the small bowel despite a normal angiographic pattern beyond 3 h of obstruction and successful lysis. The results demonstrate that angiography alone is of poor predictive value in determining bowel viability in acute intestinal ischemia.