The dissolution of planar, cylindrical, and spherical particles in a stagnant liquid is analyzed theoretically. Assuming that the diffusion of solute molecules is the rate-determining step, the temporal variation in the particle size is derived. The transient nature of the phenomenon under consideration is taken account of by solving a moving boundary problem through regular perturbation, and a perturbation parameter assessing if the pseudo-steady state assumption made in previous analyses is proposed. The applicability of the analytical result derived is verified by fitting it to the experimental data in the literature. We show that neglecting that transient nature may yield appreciable qualitative and quantitative deviations, especially if a particle has a high solubility, large molecular weight, or low density. (C) 2014 Elsevier Ltd. All rights reserved.