Experimental values of densities (rho) and speeds of sound (u) at T = (298.15, 303.15, and 308.15) K while the viscosities (eta) at T=298.15 K in the binary mixtures of I-octanol with n-hexane, n-octane, and n-decane are presented over the entire composition range of the binary mixtures. Using these data, excess molar volumes (V-m(E)), viscosity deviation (Delta eta), deviation in speeds of sound (Delta u), deviation in isentropic compressibility (Delta K-s), excess free volume (V-f(E)), and excess Gibbs free energy of activation of viscous flow (Delta G(.E)) are calculated and presented graphically. All the computed quantities are fitted to a polynomial equation. The values of V-m(E) have been analyzed using Prigogine-Flory-Patterson (PFP) theory. Furthermore, the theoretical values of speed of sound (u) and isentropic compressibility (k(s)) have also been estimated using the Prigogine--Flory-Patterson (PFP) theory with the van der Waals (vdW) potential energy model and the results have been compared with experimental values. The experimental and calculated quantities are used to study the nature of mixing behaviour between the mixture components. (C) 2008 Elsevier Ltd. All rights reserved.