Densities of solutions of H2O in C2H5OH and D2O in C2H5OD, with a water mole fraction ranging up to 0.037, were measured with an error of 1.0 . 10 (5) g . cm (3) at T = (278.15, 288.15, 298.15, 308.15, and 318.15) K and at atmospheric pressure using a precise sealed vibrating tube densimeter. Apparent molar volumes and isobaric expansibilities down to infinite dilution of a solute were calculated. The temperature-dependent behaviour of solute H/D isotope effects on the volumetric quantities studied was analysed taking account of structure-related peculiarities of the solvating media in question. (C) 2011 Elsevier Ltd. All rights reserved.