The matrix isolation technique, using e.s.r. spectroscopy, has been employed to investigate the nature of free radical intermediates of the γ-radiolysis of polycrystalline linear and branched acyl chlorides at 77 K. The main radicals are accounted for in terms of C–H, OC–Cl, and C–COCl bond scissions and their relative abundance is significantly influenced by the chemical structure of the parent molecules. A mechanism is suggested.