Apparent molar volumes V-phi, and apparent molar heat capacities C-p,C-phi were determined for aqueous solutions of D-lactose (.) H2O at molalities (0.01 to 0.34) mol (.) kg(-1) at temperatures (278.15 to 393.15) K, and at the pressure 0.35 MPa. Our V-phi values were calculated from densities obtained using a vibrating tube densimeter, and our C-p,C-phi, values were obtained using a twin fixed-cell, power-compensation, differential-output, temperature-scanning calorimeter. Our results for D-lactose(aq) and for D-lactcose (.) H2O were fitted to functions of m and T and compared with the literature results for aqueous D-glucose and D-galactose solutions. Infinite dilution partial molar volumes V(2)degrees and heat capacities C(p,2)degrees are given over the range of temperatures. (C) 2004 Elsevier Ltd. All rights reserved.