Microscopic dynamics of salicylate (Sal(-)) anions in long rodlike or threadlike micelles formed by cetyltrimethylammonium bromide (CTAB) and sodium salicylate in aqueous solution was examined by use of magnetic nuclear resonance (NMR) spin-lattice relaxation time (T-1) measurement. Molecular motions of Sal(-) anions are remarkably restricted in the threadlike micelle. The rotational correlation times for the Sal(-) anion estimated from the T-1, by taking into account only intramolecular dipole-dipole interaction, are in good agreement with those previously estimated from fluorescence anisotropy. Rotational motions of free Sal(-) anions in aqueous solution are slightly anisotropic presumably because their molecular shape is not spherical. Within the threadlike micelle, however, tumbling motions of the Sal(-) anion are highly restricted due to the fact that the Sal(-) anion is electrostatically restrained by CAT(+) cations. Molecular motions of the CTA(+) cation in the micelle are also highly restricted. The rotational correlation time for the CTA(+) cation in the micelle is not affected by the concentration of the free Sal(-) anion, although its concentration has a strong effect on rheological behavior. Thus, the microscopic motions and some related physical parameters, such as the persistence length of the micelle, are essentially independent of the concentration of the free Sal(-) anion once the threadlike micelle is formed.