A review is given of the problem of passage of charged particles through a crystal lattice and determination of the location of foreign atoms inside the unit cell. Chapter 1 is introductory. Chapter 2 considers the effect of spatial redistribution of the flux of charged particles in axial channeling. The effect of multiple scattering on the flux at both large and small depths is discussed. A relation is demonstrated between the location of the foreign atoms and the location of the peaks in the angular distribution. Chapter 3 considers the redistribution of the flux and multiple scattering in planar channeling. Chapter 4 is devoted to channeling of heavy ions. A technique is presented for calculation of the spatial redistribution of implanted ions with inclusion of the channeling effect. Chapter 5 presents a review of experiments on determination of the location of foreign atoms inside the unit cell.