Benzene phosphorus dichloride can be prepared by the reaction of benzene and phosphorus trichloride in the presence of a catalytically effective amount of a Friedel-Crafts catalyst, such as aluminum trichloride or ferric trichloride, at elevated temperature, such as from about 200.degree. C. to about 250.degree. C., and superatmospheric pressure, such as no less than the vapor pressure of the components at the chosen reaction temperature, to insure a liquid reaction medium.