The ability of eight ring current models to explain the large conformation-dependent shifts observed for the nuclear magnetic resonance signals of protons in the immediate vicinity of the heme ring in reduced cytochrome c is investigated. These models are based on the dipolar, Johnson-Bovey, and Haigh-Mallion equations. The two cases of the Johnson-Bovey equation based on a five-current-loop model and the Haigh-Mallion equation are shown to be the most advantageous. The dipolar equation leads to poorer predictions; this is attributable to the breakdown of the point-dipole approximation in regions physically accessible to protons outside the aromatic ring. This finding is in contrast to the situation with nonheme proteins where all three equations lead to results of similar validity. A full prediction of the NMR spectrum of cytochrome c is briefly reported. Its main limitation is the level of refinement of the crystallographic coordinates. © 1980.