Biomass pyrolysis technologies often process an assortment of biomass forms determined by availability and cost. To support the screening of diverse biomass forms for utilization in pyrolysis, NEA developed detailed reaction mechanisms to predict the complete distributions of all major products from any biomass form. Separate mechanisms describe primary devolatilization at heating rates fast enough to prevent tar deposition within the fuel, and secondary volatiles pyrolysis of tar, first, into PAH and, ultimately, into soot with simultaneous elimination of heteroatoms as noncondensables. These mechanisms predict the yields of tar, aromatic oils, light oxygenates, C 1 – C 4 hydrocarbons, soot, CO, CO 2 , H 2 O, H 2 , NH 3 , and H 2 S, plus the tar MWD and the elemental compositions of tar, soot, and char. The kinetics cover the domain of temperature (300-1200C), pressure (<1 – 50 atm), and transit times in advanced fluidized bed and entrained flow processing technologies. This paper emphasizes the validation of predicted product distributions with test data from lab-and pilot-scale facilities. Our validation database represents 2 cellulose samples, 7 woods and wood wastes, and 4 agricultural residues, and covers nearly the entire domain of elemental composition for biomass. One dataset completely covered the conversion of tar from two cellulose samples, and another determined the complete distributions of all major products from four diverse biomass samples with very good mass and elemental balance closures. Transient and temperature-dependent tar yields from all samples were simulated within the measurement uncertainties, with only a few stray discrepancies. Our kinetic analysis depicts the broad maxima in tar yields with temperature for the wood samples and cellulose, as well as the sharper maxima for corn stover, bagasse, red maple, and wheat straw. For every biomass sample, the correct temperature for maximum yield is apparent in the simulations, except for wheat straw.