Two cases of patients with Crohn's-like colitis and glycogen storage disease Ib have been reported previously. In the current report, chronic inflammatory bowel disease that developed in another adolescent with this glycogenosis is described, thereby corroborating the association. The neutrophil dysfunction observed in glycogen storage disease Ib is the most likely predisposing factor. Neutrophil function was investigated in our patient in an attempt to shed light on the pathogenesis of his intestinal inflammation. The patient displayed reduced neutrophil chemotaxis to zymosan-activated serum, N-formyl-methionine-phenylalanine, and Escherichia coli bacteria-derived factor and reduced intracellular killing of Staphylococcus aureus 502A. Others have found this defective bacteriocidal activity to be caused by impaired oxidative metabolism. The recent recognition of chronic inflammatory bowel disease in glycogen storage disease Ib, as well as in chronic granulomatous disease, suggests that further study of respiratory burst activity of neutrophils in Crohn's disease is warranted.