The effect of pressure on the volume in the liquid phase for chlorobenzene and 1,2-dichlorobenzene has been measured relative to their volumes at 0.1 MPa with a bellows volumometer for pressures up to 300 MPa over the temperature range (278.15 to 338.13) K. The experimental volume ratios have been represented by two sets of equations to enable interpolation and extrapolation of volumetric properties. The results of one of these representations suggests a means of extrapolating the volumetric properties of these chloro-substituted benzene derivatives. Isothermal compressibilities, thermal expansivities, normalized volume fluctuations, and the change in the isobaric heat capacity from its value at 0.1 MPa have been calculated from the results.