99mTc-pyrophosphate was investigated for use as an indictor of intestinal infarction in intussuscepted bowel. Irreducible intusseusceptions were created in 18 rabbits by surgery. 99mTc-pyrophosphate was then injectedintravenoulsy 6-12, 18, 24 and 30-40 hours later for external scanning. In 15 of the rabbits, infarction developed with intussusception, and 13 of them demonstrated increased uptake of 99mTc-pyrophosphate on external in vivo scintiscans. The remained 2 of them showed no evidence of increased uptake. So false negative cases were 2(sensitivity 86.7%). The3 rabbits without infarction showed no increased uptake of raidonuclide. Specimen scanning confirmed increased uptake of raionuclide in the infarcted segments. These observations suggest that 99mTc-pyrophosphate is a reliable indicator or the intestinal infarction that sometimes occurs with intestinal intussusception.