A new N-15 constant-time relaxation dispersion pulse scheme for the quantification of millisecond time-scale exchange dynamics in proteins is presented. The experiment differs from previously developed sequences in that it includes H-1 continuous-wave decoupling during the N-15 Carr-Purcell-Meiboom-Gill (CPMG) pulse train that significantly improves the relaxation properties of N-15 magnetization, leading to sensitivity gains in experiments. Moreover, it is shown that inclusion of an additional N-15 180 degrees refocusing pulse (phase cycled +/- x) in the center of the CPMG pulse train, consisting of N-15 180(y)degrees pulses, provides compensation for pulse imperfections beyond the normal CPMG scheme. Relative to existing relaxation-compensated constant-time relaxation dispersion pulse schemes, v(CPMG) Values that are only half as large can be employed, offering increased sensitivity to slow time-scale exchange processes. The robustness of the methodology is illustrated with applications involving a pair of proteins: an SH3 domain that does not show millisecond time-scale exchange and an FF domain with significant chemical exchange contributions.