The relative permittivities, epsilon(r), and refractive indices, n(D), have been measured over the whole composition range for binary mixture propylene carbonate + toluene at temperatures from 283.15 K to 313.15 K. The relative permittivity of the mixture increased monotonically by addition of propylene carbonate. Calculated deviations in relative permittivity, Delta epsilon(r), were always negative showing a minimum. From the values of epsilon(r) and n(D), the molar polarizability, P-m, has been calculated from the Kirkwood-Frohlich equation and the deviation in molar polarizability, Delta P-m, has been estimated. Molar refractivity, R-m was also calculated.