The in vitro function of neutrophil granulocytes from 11 patients with Crohn's disease was studied. Nitroblue tetrazolium reduction test results were normal in all patients. Increased intracellular survival of Staphylococcus aureus, impaired glucose-1-14C metabolism of the granulocytes at rest and during phagocytosis, and reduced and delayed staphylococcus-induced granulocyte chemiluminescence response were recorded in the patients with Crohn's disease, a defect that may be involved in the pathogenesis of the chronic granulomatous inflammatory response in this disease.