Because of the importance that the energy use of agricultural and forestry wastes has acquired over the last years, results for the laminar flame speed of producer gas coming from the gasification of lignocellulosic biomass are presented in this work. These results have great interest for the development of combustion models that provide significant information to be used as a tool for the optimization and design of specific internal combustion engines. The CHEMKIN software, together with the GRI-Mech chemical reaction mechanism, has been used to compute the laminar flame speed for different producer gas compositions, different values of pressure and temperature, and different producer gas/air equivalence ratios. The results have been compared with those obtained in an experimental combustion bomb, as well as with the laminar flame speed obtained for conventional fuels, showing that the flame speed of the producer gas is less than that of isooctane but greater than that of methane. A sensitivity analysis shows the influence that the dominant chemical reactions and species have on the laminar flame speed of producer gas at different producer gas/air equivalence ratios. Although good qualitative agreement has been found, some differences between experimental and modeled results at high pressure and temperature are due to the instabilities in the experimental flame.