NMR spectroscopy is the method of choice to measure protein and nucleic acid dynamics on a variety of timescales. Picosecond to nanosecond dynamics can be precisely probed by quantifying R1 and R2 relaxation rates and heteronuclear NOE values, whereas residual dipolar couplings (RDCs) are sensitive to motion on a wide range of timescales from sub-microseconds to milliseconds. Even slower dynamics can be assessed by hydrogen exchange experiments. In a biochemical context, relaxation dispersion NMR spectroscopy is particularly valuable because it reports on the biologically important timescale from micro- to milliseconds, encompassing the conformational rearrangements of ligand binding, enzymatic reactions, and base-pair transitions. From relaxation dispersion measurements, it is possible to obtain structural, kinetic, and thermodynamic information about energetically excited conformational minor states beyond the ground-state structure. Here, we review the two methods of R1ρ and R2 relaxation dispersion, focusing on recent developments in pulse sequence design and data processing techniques, as well as applications of the methods to resolve protein–protein interactions.