C-13 spin-lattice relaxation times (T-1) and nuclear Overhauser enhancement (NOE) factors have been measured at three magnetic field strengths (corresponding to resonance frequencies of 22.5, 75, and 100 MHz) for the DNA-binding Ligand Hoechst 33258. This molecule comprises two benzimidazole moieties, an N-methylpiperazine ring and a phenol ring, and adopts an anisotropic curved shape that assists in its binding to the minor groove of DNA. The C-13 relaxation data were interpreted in terms of various models for molecular motion. It was determined that in solution the molecule tumbles anisotropically and that there is a significant degree of internal motion associated with both the phenol and piperazine moieties. Models which involve the rapid jumping of C-H moieties between conformational states provided a good fit to the relaxation data, as did the model-free approach of Lipari and Szabo (J. Am. Chem.;Soc. 1982, 104, 4546).