  The simulation methods for the channeling phenomena in GeV/TeV energy range
in ideal or distorted crystal lattices are discussed. Monte Carlo predictions
for feed-out and feed-in rates, dislocation dechanneling, and deflection
efficiencies of bent crystals are compared to the experimental data. The role
of multiple interactions with crystal in circular accelerators ("multipass
channeling") for the efficiency boost in the crystal-aided extraction
experiments is analysed. Possible future applications of the crystal channeling
technique are considered.
