Drastic decreases in the thermal conductivity upon deformation similar to those reported by Sproull, Moss, and Weinstock have been found in NaCl, KCl, and NaF crystals. Unexpected differences in the frequency dependence of the phonon—defect relaxation times lead to an investigation of whether point defects, created during the deformation, might influence the phonon scattering. Studies of the recovery kinetics of the thermal conductivity paralleling those carried out on the mass density changes by Silverstone and Pratt on NaCl, and Vaughanet al.on KCl, seemed to exclude this. Experiments on bent LiF further supported the view of Sproullet al.that the thermal conductivity of deformed alkali halides is determined by coherent scattering of phonons off groups of dislocations.