A variety of optical absorption, emission and luminescence excitation spectra have been measured in an attempt to identify the centers involved in the thermoluminescence of commercial LiF:Mg. It is concluded that the principal trapping centers consist of a hole trapped near various groupings of Mg2+ions and vacancies. The optical absorption bands of these centers occur in the 3100–3800 Å region which contains several absorption bands corresponding to different geometries of the centers. It is suggested that the 2200‐Å band arises from Mg2+ion‐vacancy complexes which have captured two holes. During thermoluminescence, holes are transported from traps to emitting centers. The luminescent center appears to be theFcenter both in an isolated position and when adjacent to a complex involving Mg2+ions.