The real part of the complex relative electric permittivity, epsilon(r).(T, p), of liquid methylbenzene has been determined with an estimated expanded relative uncertainty of +/-0.018 % from measurements of the complex capacitance of a concentric cylinder capacitor at temperatures between (293 and 393) K and pressures below 60.6 MPa. The measurements were corrected for the isothermal compressibility of the solid that formed the capacitor. The isothermal compressibility was determined by comparison of measurements of epsilon(r)(He, 303 K and 393 K, p) with ab initio results from quantum mechanics. The epsilon(r)(T, p) values obtained for methylbenzene were combined with the amount-of-substance density, rho, which was obtained from the equation of state reported by Lemmon and Span (J. Chem. Eng. Data 2006, 51, 785-850), to calculate the molar polarizability, P, that was fit with an expanded (k = 2) relative uncertainty of +/-0.03 % by three parameters. The epsilon(r)(T, p) reported by Kandil et al. (J. Chem. Eng. Data 2008, 53, 1056-1065) from measurements with a radio frequency re-entrant cavity, a technique with entirely different sources of systematic error, were converted to P.rho and they differed from 1.10(-3) at T = 290 K to -2.5.10(-3) at T = 406 K (with < P.rho > approximate to 0.31 giving a relative difference of between 0.3 % and -0.8 %, respectively) at temperatures that overlap ours. At T = 298 K the measurements reported by Mospik (J. Chem. Phys. 1969, 50, 2559-2569) at a pressure between (0.1 and 20) MPa when converted to the product P.rho are within -0.8.10(-3) (a relative difference of about -0.26 %) of our smoothing equation while at T = 273 K, about 20 K below our lowest temperature, the differences for P.rho are -0.4.10(-3) (a relative difference of about -0.13 %).