Molecular dynamics of metabolites are important for their interactions and functions. To understand the structural dependence of molecular dynamics for N-methylated glycines, we comprehensively measured the (13)C and (1)H spin-lattice relaxation times for sarcosine, N,N-dimethylglycine, betaine, and betaine hydrochloride over a temperature range of 178-460 K. We found that the reorientations of methyl groups were observed for all these molecules, whereas reorientations of whole trimethylamine groups were detected in betaines. While similar rotational properties were observed for methyl groups in N,N-dimethylglycine and those in betaine, three methyl groups in betaine hydrochloride had different motional properties (E(a) approximate to 20.5 kJ/mol, tau(0) approximate to 1.85 x 10(-13) s; E(a) approximate to 13.9 kJ/mol, tau(0) approximate to 2.1 x 10(-12) s; E(a) approximate to 15.8 kJ/mol, tau(0) approximate to 1.1 X 10(-12) s). N,N-Dimethylglycine showed a phase transition at 348.5 K with changed relaxation behavior for methyl groups showing distinct E(a) and tau(0) values. The DIPSHIFT experiments showed that CH(3) and CH(2) moieties in these molecules had dipolar-dephasing curves similar to these moieties in alanine and glycine. The activation energies for CH(3) rotations positively correlated with the number of substituted methyl groups. These findings provided useful information for the structural dependence of molecular dynamics for N-methylated glycines and demonstrated solid-state NMR as a useful tool for probing the structure-dynamics relationships.