A model is developed to explain the devolatilization (pyrolysis) behavior of softening coals. A brief review of currently existing devolatilization models indicates that many totally disregard the importance of mass transfer limitations in and around pyrolyzing coal particles. Many that do account for mass transfer limitations do so via a pore diffusion model which is inappropriate for softening coals. The present model develops a concept of a softened, “evaporating” coal particle with attention paid to the details of the chemistry occurring in the “metaplast” (tarry mass of the particle). Specifically, a quantitative approach incorporates metaplast repolymerization and cracking reactions within the particle. The results suggest important differences in modeling of coal pyrolysis data obtained at atmospheric and vacuum conditions.