An elementary model for the dissolution of pure hydrate in undersaturated water is proposed that combines intrinsic decomposition within a desorption film and the subsequent diffusion of the released hydrate guest species into bulk water. Applying the proposed approach to recently published measurements of the decomposition rates of methane (CH4) and carbon dioxide (CO2) hydrates in deep seawater suggests that the concentration of the hydrate guest species at the interface between desorption film and diffusive boundary layer may be much lower than ambient solubility. Calculations, however, fail to account for the observed proportionality of decomposition rate with solubility for both CH4 and CO2 hydrates. This may indicate a limitation in the range of applicability of published formulas for intrinsic hydrate decomposition rates. (c) 2005 Elsevier Ltd. All rights reserved.