Infrared spectra of ethanol in low-temperature argon and xenon matrices were measured with an FT-IR spectrometer. The relative intensities of the IR bands for anti and gauche conformers changed according to the Boltzmann distribution law, when the matrix temperature was varied in the ranges between 15 and 30 K in argon and between 15 and 55 K in xenon. The energy difference between the two conformers was determined from the spectral changes to be 29.4 +/- 2.1 cm(-1) in argon and 20.0 +/- 1.2 cm(-1) in xenon, where anti is more stable than gauche. The results are discussed in terms of the interaction between an ethanol molecule and noble-gas atoms. (C) 2011 Elsevier B. V. All rights reserved.