Excess molar volumes V-m(E) for binary mixtures of acetonitrile + dichloromethane, acetonitrile + trichloromethane, and acetonitrile + tetracloromethane at 25degreesC have been used to calculate partial molar volumes (V) over bar (i), excess artial molar volumes (V)over bar>(E)(i), and apparent molar volumes V-phii of each component as a function of composition. The V-m(E) values are negative over the entire composition range for the systems studied. The applicability of the Prigogine-Flory-Patterson theory was explored. The agreement between theoretical and experimental results is satisfactory for the systems with dichloromethane and tetrachloromethane. For the unsymmetrical behavior of the system with trichloromethane, however, the agreement is poor.325417434