Formation of ESR-detectable free radical adducts due to ethanol administration is blocked in NADPH oxidase–deficient mice. Wild-type mice and p47^phox, respectively, were fed enteral high-fat control diet (a, b) or enteral high-fat ethanol-containing diet (c, d) for 4 weeks. After POBN injection (1 g/kg intraperitoneally), bile was collected and analyzed using ESR spectroscopy. Representative ESR spectra of seven separate experiments are shown.