Nuclear magnetic resonance (NMR) is a powerful technique capable of monitoring a wide range of motions in proteins on a per residue basis. A variety of 2 H relaxation experiments have been developed for monitoring side-chain methyl group motions on the picosecond-nanosecond timescale. These experiments enable determination of the order parameter, S 2 axis , which reports on the rigidity of the C-CH 3 bond for side-chain methyl groups. The application of a commonly used subset of these experiments is described in this chapter. It is intended to serve as a practical guide to investigators interested in monitoring side-chain motions. © 2014 Springer Science+Business Media,New York.