Metabolism of 2,6-diisopropylnaphthalene (2,6-DIPN) in rats was found to proceed exclusively through oxidation of the isopropyl chain of the molecule. Five unconjugated metabolites were isolated from the urine and identified: 2,6-naphthalenedi(2-propan)-2-ol, 2-[6-(1-hydroxy-1-methyl)ethylnaphthalen-2-yl]-2-propionic acid, 2,6-naphthalenedi-2-propionic acid, 2-[6-(1-hydroxy-1-methyl)ethylnaphthalen-2-yl]-2-hydroxypropionic acid, and 2-[6-(1-hydroxy-1-methyl)ethylnaphthalen-2-yl]-1,2-propanediol, together with a small amount of the unchanged compound. The identification of these metabolites was made by means of mass, infrared, and nuclear magnetic resonance spectrometry. The presence of glucuronides of five metabolites described above was also suggested by thin-layer and gas-liquid chromatography of the extract that was obtained after hydrolysis by beta-glucuronidase. In addition, the quantitative determination of metabolites indicated that these five were the major urinary metabolites of 2,6-DIPN, and that the total urinary excretion of these metabolites in 24 hr after administration was about 23% of the dose.