The consequences of irradiating Ø 1" x 1" LaBr3: 5%Ce crystals with 0.1-100kGy gamma radiation have been investigated. The material displays lower photoelectron yield and poorer energy resolution after exposure to a Co-60 source. The magnitude of the damage is larger in a packed scintillator. In addition to a prompt effect following gamma irradiation, consisting of a deterioration in both photoelectron yield and energy resolution, there is a delayed effect over a timescale of several days, resulting in a further decrease of yield, but accompanied by a partial recovery of resolution. (C) 2007 Elsevier Ltd. All rights reserved.