&NA;The experience with 6299mTc‐labeledin vivoscans performed for lower gastrointestinal bleeding is discussed. Thirty‐seven scans were deemed positive. The tendency of scans to become positive correlated with observations of active bleeding. Five patients had fulminant hemorrhage, necessitating emergency operation. In this group, scanning accurately located the bleeding sources prior to intervention. Seven other patients having later operations bled less rapidly. The bleeding site was localized accurately by scanning in three of these patients. Two studies were falsely positive and two were negative, whereas angiography was positive in two patients studied.Labeled RBC scanning is a useful technique in the early evaluation of patients with lower gastrointestinal bleeding, obviating the need of arteriography in some cases.