With the recent development of positron channeling as a technique to spatially sample electrons in crystals [1,2], it would be imperative to investigate positron dechanneling in crystals. Scattering of aligned positrons will be considered due to thermal vibrations and electronic collisions. Based on steady increase approximation of transverse energy, axial dechanneling calculations of MeV positrons will be performed for a well collimated beam and perfect crystal.