Loran-C and –D phase corrections are developed for propagation over irregular, inhomogeneous ground. The effect of the receiver altitude above the sea-level sphere, altitude of the ground above the sea-level sphere, and variation in the electrical constants of the ground along the propagation path are considered. A strong amplitude and phase perturbation is noted as the observer (aircraft) passes over a ridge. This perturbation is not negligible at altitudes attainable by conventional aircraft. The perturbation is most severe on the surface of the ground but decreases somewhat with altitude. A secondary effect, which is not negligible, is caused by conductivity changes along the propagation path. In general, it can be concluded that the classical ground-wave theory becomes useless in the presence of severe departures from the sea-level sphere and the new theory presented in this paper must be employed to predict a hyperbolic line of position for Loran-C or –D. It is also noted that the classical theory can be recovered numerically as a special case of this more general treatment of ground wave propagation.