Waves with frequencies satisfying &ohgr;1+&ohgr;2=&OHgr; can heat ions. In this nonlinear interaction mechanism, coupling of a wave with frequency &ohgr;1 and an ion trajectory, distorted by a wave with frequency &ohgr;2, results in a force varying at the gyrofrequency &OHgr; at the ion position. The heating rate, verified by test particle calculations, is found for both broadband and coherent waves in the small gyroradius limit and is applied to ion conics above the auroral zone. This heating mechanism may be significant in other geophysical and astrophysical environments.