Retrospective studies, based on autopsy findings, indicate that infiltration of the gastrointestinal tract complicates leukemia of all types and may be present from the esophagus to the rectum. This report presents what is believed to be the first reported case of a patient with chronic lymphocytic leukemia with evidence of esophageal, gastric, duodenal bulb, and colonic involvement confirmed by mucosal biopsy at endoscopy.