The influence of segmental small intestinal ischemia on the central circulation and on the regional blood flow to consecutive segments of the small intestine in the rat was investigated with the microscphere method. Ischemia was established by ligating 11 arterial mesenteric end arcades, corresponding to one quarter of the total length of the small intestine. The blood supply to different organs and central circulatory variables were determined before, and 10 min, 30 min, 2 h and 14 days after the establishment of the ischemia. After 10 min of ischemia, there was an increase of the blood flow to the segments distal to the ischemic region but after 30 min, this blood flow was the same as the control flow. The central circulatory variables weere not affected. After 2 h of ischemia, the blood supply to both the ischemic and the non-ischemic part of the small intestine had deteriorated considerably. Thus, the vascular resistance in the ischemic segments and the segments surrounding it was increased. Cardiac output was reduced by about 50%. In the experimental group investigated 14 days after establishment of the ischemia, the mortality rate was about 50%. In the survivors, the intestinal blood supply had returned to normal.