Introduction During the past half-century the management of intestinal obstruction has undergone significant improvement; however, strangulation continues to represent a serious complication. Silen and associates8 recently reviewed 480 cases of intestinal obstruction and found an over-all mortality rate of 10.5%. When strangulation was present 21.4% died, whereas with simple obstruction the mortality rate was 7.3%. Thus, strangulation imposes a serious threat to the patient with intestinal obstruction, and medical measures, including intestinal decompression, fluid and electrolyte replacement, and antibiotic therapy, have not reduced the mortality rate appreciably. Extensive investigation into the nature of toxicity in strangulation obstruction has been in progress for years1-3,6,7,9 and eventually may provide an answer to this perplexing problem. Another approach involves the earlier recognition of strangulation during a stage when surgical intervention might be expected to prevent progression to infarction. The present study demonstrates that isotopelabeled serum albumin concentrates in the fluid which