A number of DSC studies have determined the onset temperature and the enthalpy change for the beta -> gamma phase transformation in plutonium but these have all been conducted by measuring the phase transformation parameters immediately following the alpha -> beta phase transformation which will have a considerable impact on the reaction kinetics. The thermal history and condition of a specimen will have a significant effect on the reaction parameters of a solid phase transformation. The current study examines the influence of the specimen condition and more specifically the impact of a previous phase transformation and the mode of formation of the beta-phase from both the alpha-phase and from the gamma-phase on the beta -> gamma phase transformation parameters and reaction kinetics. The impact of the beta-phase condition on the transformation parameters of the beta -> alpha phase transformation is also examined. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.