Biomass pyrolysis experiments were carried out in a fluidized bed reactor (FBR) and char yields were measured for three soft woods, three hardwoods, two herbaceous plants and three agricultural residues. Pyrolysis conditions included slow (10 K center dot min (1)) and rapid (max. around 1000 K center dot s (1)) heating rates and a temperature range between 573 K and 1473 K. Rapid pyrolysis tended to give lower char yields than slow pyrolysis for Eucalyptus camaldulensis (hardwood), Japanese cypress (softwood), switchgrass (herbaceous plant) and bagasse (agricultural residue). Under rapid pyrolysis conditions, char yields from softwood species were lower than those from other biomass species. Cross sections of char from Japanese cypress and Eucalyptus camaldulensis were also observed by SEM, and the effects of temperature, heating rate and type of biomass on char structure were investigated.