This Bureau of Mines report analyzes diverse observations of the rates and mechanisms for the pyrolysis and devolatilization of coal and polymethylmethacrylate (pmma). New data are presented for pmma, together with new morphological evidence for the microscopic structure of the pyrolysis and devolatilization wave front in coals. It is concluded that there is no substantive evidence to support the traditional viewpoint that the pyrolysis and devolatilization rate process occurs isothermally, under chemical rate control; or is described realistically by a classical, unimolecular arrhenius function of temperature. Instead, the reaction process occurs as a highly nonisothermal, heat-flux-driven, pyrolysis and devolatilization wave front, whose speed of propagation is predictable by internal heat transport constraints. Except for the complication of its char-layer residue, whose increasing thickness insulates the pyrolysis wave front from the heat source flux that drives it, both coal and pmma behave similarly during pyrolysis and devolatilization. For pmma, decomposition occurs at a temperature of 350 deg. to 550 deg.C; for coal it occurs at 450 deg. to 600 deg.C. There is no evidence that the reactant temperature ever exceeds those values regardless of the source temperature to which the samples are exposed.