Abstract Channeling of 100 keV protons along the c-axis in ice has been measured in 150° backscattering between −165 and −60°C with an energy resolution of 5 keV (FWHM), corresponding to a depth resolution of 250 A. A clean surface, with a disorder extending to less than 3 molecular diameters, is obtained above -75°C by evaporation with a rate of 400 A/s or more. The critical angle (half width of the scattering yield dip at half depth) is 0.8° and near the surface the minimum yield for an aligned proton beam is (11±1) per cent. These results, can be explained by Lindhard's theory, but the large thermal motion ofthe hydrogen nuclei reduces the atom correlation along the rows and increases the minimum yield. Below -110°C and without evaporation, radiation damage occurs in the bulk, while channeled irradiation produces a disordered layer near the surface. This layer is eliminated by sputtering with random irradiation. Water vapour deposition has been identified at −157°C by analysis of the energy spectrum wi...