The magnetopause and boundary layer are typically characterized by large amplitude transverse wave activity with frequencies below the ion cyclotron frequency. The signatures of the transverse waves suggest that they are kinetic Alfv¿n waves with wavelength on the order of the ion gyroradius [Johnson and Cheng, 1997a; Johnson et al., 2001>. We investigate ion motion in the presence of large amplitude kinetic Alfv¿n waves with wavelength the order of &rgr;i and demonstrate that for sufficiently large wave amplitude (ΔB⊥/B0 > 0.05) the particle orbits become stochastic. As a result, low energy particles in the core of the ion distribution can migrate to higher energy through the stochastic sea leading to an increase in T⊥ and a broadening of the distribution. This process can explain transverse ion energization and formation of conics which have been observed near the magnetopause in both the magnetosheath and low-latitude boundary layer. ¿ 2001 American Geophysical Union