Apparent molar volumes, V-2,V-phi, and viscosities, eta, of disaccharides D-(+)-maltose monohydrate, D-(+)lactose monohydrate, sucrose, and D-(+)-cellobiose in water and in (0.49850 and 0.99705) mol . kg(-1) aqueous solutions of ammonium sulfate {(NH4)(2)SO4} have been determined from density, p, and efflux time, t, measurements, respectively, at temperatures (288.15, 298.15, 308.15, and 318.15) K. The refractive indices, n(D), for these systems have also been determined. From these data, the standard partial molar volumes, V-2(infinity), at infinite dilution and viscosity B-coefficients (using the Jones-Dole equation) have been determined at different temperatures. The standard partial molar volumes of transfer, Delta V-t(2)infinity, and B-coefficients of transfer, Delta B-t, have been estimated for the transfer of disaccharides from water to aqueous ammonium sulfate solutions. Partial molar expansion coefficients, (partial derivative V-2(infinity)/partial derivative T)(P) and (partial derivative V-2(2)infinity/partial derivative T-2)(P), and dB/dT coefficients have also been estimated. Gibbs free energy of activation of viscous flow has been calculated by using Feakin's transition-state theory for the studied systems. The various parameters have been utilized to rationalize the hydration behavior of disaccharides.