Bactericidal activity of phagocytic cells depends largely upon their production of highly reactive compounds via the metabolism of oxygen. A lesion anywhere in the biochemical pathway of hydrogen peroxide production potentially can cause chronic granulomatous disease (CGD). Recent work has shown that CGD results from specific abnormalities in the nicotinamide-adenine dinucleotide phosphate (NADPH) system, which includes membrane-associated proteins, NADPH, cytochrome b-558, and several cytosolic proteins. Pharmacologic alteration of phagocytic oxidative metabolism can now be achieved through use of recombinant interferon-gamma (IFN-gamma). Data from a multicenter clinical trial indicate that sustained administration of IFN-gamma is effective in the management of CGD; for patients who received IFN-gamma, a 72% reduction in the relative risk of serious infection was noted in comparison with the risk for patients who received placebo. IFN-gamma reduced not only the number of serious primary infections but also the length of hospitalizations.