Within the basic description of Lindhard a theoretical model of axial dechanneling starting from the master equation for transverse energy distribution is developed. In contrast to the diffusion model, large changes in transverse energy are included which are of special importance for defects. Numerical results of the minimum backscattering yield for perfect crystals, crystals with point defects and crystals with dislocations show good agreement with experimental data for different temperatures and energies. This is the basis for the application to defect analysis. For point defects the measurement of temperature dependence of the minimum yield proved to be a very suitable method for the determination of preferred lattice positions if they are not too far from the string (⩽ 0.07 nm in silicon).