Solvent-free esterification of wood with octanoyl chloride produced an esterified material with a weight increase. of 87% and an ester content of 60%. However a fraction of sawdust (22% of the esterified wood) was solubilized during this esterification. Chemical analyses showed that it contained essentially esterified and hydrolyzed hemicelluloses with small amount of esterified cellulose. The reactivities of oakwood sawdust and wheatbran hemicelluloses were compared under different reaction conditions. Pure hemicelluloses were more reactive and more readily hydrolyzed (without using solvent) than sawdust, to give esterified oligomers and polymers with a high degree of substitution and which were solubilized (48% of the esterified hemicelluloses) in the reaction medium. The use of pyridine as a toxic solvent the acid hydrolysis of the polysaccharides and therefore their solubilization.