It is shown that a conventional two-site magnetization-transfer experiment provides an insufficient amount of information to allow a reliable determination of the exchange rate, unless | λ 2| ⪢ | λ 1|, where λ 1 and λ 2 are the time constants of the two exponentials involved. This difficulty, which is often met, is further hampered when the linewidths as well as the longitudinal relaxation rates of the two exchanging signals are different, when a perturbation of the noninverted signal occurs, or when the signal intensities are difficult to determine. However, by including a complementary experiment, in which the perturbed and unperturbed signals are interchanged, additional, independent information about the parameters involved is provided, allowing all of the unknown parameters including the exchange rate to be determined in most cases. The significant increase in the applicability of the technique when the complementary experiment is included, as well as the considerable errors that may be introduced when it is omitted, is illustrated by examples of the rate of exchange between the NH and H 2O protons in the water/ N-methylacetamide system. In addition these experiments demonstrate that exchange rates covering about three orders of magnitude (0.06 to 45 sec −1) can be determined by the method when applied in the form presented here, as exchange rates which are at least seven times slower than the fastest relaxation rate can be evaluated.