Abstract A Computer program for following the trajectories of high energy ions in a fcc-lattice has been written to study the energy loss of 60 MeV 127I ions channeled between (100)- and (111)- planes of a Au-single crystal. The motion of the ions is treated classically. It is assumed that the ion has only one important interaction at a time as it moves through the lattice. The interaction potential used in the calculation is a screened Coulomb potential with a screening function derived from Thomas-Fermi-theory. The slowing down of the incident ions through inelastic encounters with the atoms of the medium is described by a stopping power function which increases exponentially with the distance from the midplane of the channel walls.