The rotational relaxation times of perchlorate ion, tau(2r), in 15 solvents and at various temperatures were determined from the measurements of the O-17 NMR spin-lattice relaxation times. The obtained tau(2r) values were much smaller than those predicted fi om the hydrodynamic model (Stokes-Einstein-Debye, SED, equation). Comparison between the observed solvent dependence of the tau(2r) value and those predicted by the continuum models, including the SED hydrodynamic model, the Hubbard-Onsager-Felderhof (HOF) electrohydrodynamic model, and the Alavi-Waltieck (AW) dielectric friction model for multipole rotation, demonstrated that solvent viscosity is an expedient indicator for representing the overall trend of the solvent dependence of the rotational relaxation time; the observed tau(2r) values showed a fractional power dependence on the viscosity (i.e., tau(2r) proportional to eta(alpha), where alpha similar to 0.25 and eta is the solvent viscosity). Site-site interactions between the perchlorate ion and solvent molecules, however, provided a significant effect on the perchlorate rotation in some solvents with a large imbalance of the electronic donor and acceptor properties (e.g., hexamethylphosphoric triamide). The values for tau(2r) calculated for alcohols (methanol, ethanol, and n-propanol) according to the HOF and the AW models were appreciably overestimated to a greater degree than those in the other solvents, and this result was ascribed to a predominant contribution from the interactions with the hydroxyl groups of the alcohols. The result of the analysis for the solvent dependence of the perchlorate rotation by the electrohydrodynamic model was also compared with that for the perchlorate translation, and the difference in the validity of the continuum models for the ionic rotation and the translation was discussed.