A method for the determination of α- and β-naph-thols in their mixtures dissolved in acetone containing chromic anhydride by nuclear magnetic resonance (NMR) technique was investigated. The signals of hydroxyl protons in the naphthols shift by varying the solvent, concentration and temperature, then their mixtures give a broad signal under the influence of the hydrogen exchange between the solutes.<BR>An acetone solution of α- and β-naphthols was found to give a well-resolved NMR spectrum of each hydroxyl proton by adding a small amount of chromic anhydride. In the above NMR spectra of naphthol mixtures, the ring proton signal appears in the region of 6.5 to 8.3 ppm and the hydroxyl proton signals appears at 8.48 ppm for β-form and 8.84 ppm for α-form. The results above mentioned show that the absorption of hydroxyl protons are free from the interference due to the ring proton absorption and the hydrogen exchange between hydroxyl protons do not occur by adding a small amount of chromic anhydride.<BR>In additional solvents containing a small amount of chromic anhydride such as, methyl ethyl ketone (MEK), ethyl acetate or ether, α- and β-naphthol mixtures were found to give well-resolved NMR spectra of hydroxyl protons for each components, but the absorption of hydroxyl protons in these solvents were found to be interfered with the ring proton absorption.<BR>In the acetone solution containing chromic anhydride, the absorption of hydroxyl protons of α- and β-form gives well-resolved NMR spectra in the concentration range 2 to 3 mol%, the separation between the two hydroxyl protons is 0.36 ppm. However the separation between the hydroxyl protons becomes smaller with an increase in the concentration, and is negligible more than 10 mol%.<BR>When the total concentration of these naphthols was held constant at 2 mol% in the mixed samples, the most well-resolved spectrum was obtained. Each calibration curve for both α- and β-naphthols was prepared by measuring the peak height ratios of the hydroxyl protons of α- to β-naphthol varying with the molar ratio.<BR>This method was more rapid and accurate than other method for the determination of naphthols and the standard deviations were 0.0055 and 0.0050 for α- and β-form, respectively.<BR>The quantity of chromic anhydride dissolved in acetone to give good results was found to be 100 to 200 ppm, and the chemical shifts of the hydroxyl protons were not observed by addition of a small quantity of chromic anhydride.