13C-N.m.r. spin-lattice relaxation measurements were used to study molecular motion in aqueous sucrose. Results show that sucrose tumbles anisotropically in solution, and that its conformation is independent of temperature and concentration. Internal rotation occurs with distinctly different rates and activation energies in the three hydroxymethyl groups. Our data are consistent with results of calculations by Bock and Lemieux who predicted that the conformation of aqueous sucrose is similar to the crystal conformation but with the loss of one intramolecular hydrogen-bond.