A laboratory scale apparatus has been developed for the direct measurement of the heat of gasification for solid fuels. The apparatus has been designed to simulate radiant energy transfer rates found under actual fire conditions and designed in such a way that the energy gains and losses with respect to the sample surfaces are well defined. Calculation of the time dependent heat of gasification for solid fuels relies on the ability to measure accurately and continuously the time dependent energy transfer rates and material responses. Tests have been conducted in which samples of polymethylmethacrylate were subjected to incident heat fluxes ranging from 1 to 4 W/square centimeter. Test results indicate that under these conditions the heat of gasification is significantly influenced by the time dependent thermal properties of the material and approaches an asymptotic value that varies with incident heat flux. Refinement of the apparatus and the testing of other materials is continuing. Results for two additional materials, fir and oak are included as Appendix A.