We consider a two-phase elastic solid subject to diffusion-induced phase transformation by interstitial hydrogen. We derive a simple analytical model to quantify the effect of misfit strain on the kinetic of phase transformation and to calculate the amplitude of the well-know hysteresis cycle observed when a sequence of forward and reverse phase transformations takes place. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.