The usual semiquantitative evaluations of temperature-dependent dipolar 13C spin-lattice relaxation times of liquid methylbenzenes (toluene, xylenes, tri- and tetramethylbenzenes), which assume isotropic molecular motion, do not allow any reliable statements to be made about the various hindered rotations of the methyl groups, and about preferred molecular rotation axes. The quantitative evaluation of the experimental data using a new formalism (complete anisotropic motion with arbitrary position of the internally rotating methyl groups) gave the following: physically meaningless results were obtained in all cases for the optimizations for one of the three possible axially symmetrical ellipsoidal motions, and in most cases for complete anisotropic motion. A quantitative evaluation of dipolar relaxation times which takes complete anisotropic motion into account is—at least for the methylbenzenes—only promising if the present 10 per cent level of experimental error in the dipolar relaxation times can be red...