AbstractPart I of this paper describes an on‐resonance, rotating‐frame relaxation method and proposes a procedure for the accurate evaluation of the contribution of chemical exchange to rotating‐frame spin‐lattice relaxation (T1p). Dynamic information, such as exchange lifetimes and chemical shift differences between exchange sites, can be extracted from the exchange contribution. The procedure extends the T1pmethod to medium‐sized and large molecules. Part II presents a verification of the T1pmethod and an analysis of experimental results. The accuracy of these dynamic parameters has been examined using simple, well‐characterized conformational exchange systems. The examination shows that T1pis convenient for studying molecular dynamics on the microsecond time scale. The application of the method to peptides and to right‐ and left‐handed DNA oligomers gives unique dynamic information on the conformational exchange processes in