Ultrasonic velocity U and viscosity eta have been measured for the binary mixture of tetrahydrofuran with 1-propanol and 2-propanol at T = 293 K, 303 K and 313 K over the entire composition range. Using these experimental data and previously reported values of density rho, excess adiabatic compressibility beta(E)(s), excess viscosity Delta eta, excess energy of activation Delta G(*E) and excess internal pressure pi(E)(i) have been evaluated. All these excess parameters were plotted against the mole fraction of tetrahydrofuran over the whole composition range. The strength and the nature of the interactions between like and unlike molecules have been discussed. (c) 2006 Published by Elsevier B.V.