Gastrointestinal bleeding has not been reported in patients with protein-losing enteropathy. The investigators describe 3 patients with protein-losing enteropathy and gastrointestinal bleeding after Fontan operations. Bleeding occurred at the onset of protein-losing enteropathy, was macroscopic, led to anemia, and required blood transfusion in all patients. Invasive testing failed to demonstrate gastrointestinal pathology as a source of bleeding. In conclusion, unexplained gastrointestinal bleeding may be part of the clinical spectrum of protein-losing enteropathy.