Excess molar volumes V-m(E) and excess molar heat capacities C-p,m(E) were determined for mixtures of benzonitrile with chlorobenzene, or benzene, or toluene al the temperatures 298.15 K and 303.15 K. For all the systems the values of V,E were negative over the whole range of compositions and values of (partial derivative V-m(E)/partial derivative T) were negative. The values of C-p,m(E) were all positive for the mixtures with chlorobenzene and toluene, while the sign for the mixture with benzene changed from positive to negative with increasing mole fraction of benzonitrile. The magnitudes of(partial derivative C-p,m(E)/partial derivative T) were small, and the sign depended on the system.