Carbon-13 relaxation times and nuclear Overhauser enhancement values were determined for the carbons of calix [4]arene in both CDCl 3 and DMSO-d 6 solvents at magnetic field strengths of 5.9, 9.4, and 14.1 T at 30 Β°C. The relaxation data for the CDCl 3 solution were well described by an isotropic motional model indicating motions in the extreme narrowing limit with a rotational correlation time of 32-38 ps. The effective shielding anisotropies for the substituted aromatic carbons were found to be in the range 150-170 ppm while the unsubstituted aromatic carbons had values in the range 180-200 ppm. In DMSO-d 6 solution, the dipolar relaxation is out of the extreme narrowing limit and it was possible to apply a Lipari-Szabo treatment of the relaxation data. This model demonstrated through the value of the generalized order parameter, S 2 , a slight increase in the range of motion for the aliphatic CH 2 carbon over the unsubstituted aromatic carbons. It was not possible, however, to determine reliable values for the effective shielding anisotropies for the aromatic carbons. An earlier report of carbon-13 relaxation for calix[4]arene in CDCl 3 had indicated distinctly different relaxation times for the two unsubstituted aromatic carbons. We found virtually identical relaxation times for both carbons at all three magnetic fields used in this study.