The scaling up of the pressurized hot water flow-through extraction system for biomass from the laboratory scale to the pilot scale by a factor of 6000 was studied. The extraction efficiency and system performance were evaluated by comparing the hemicellulose extraction kinetics, yield, and mass balances. The extractions were performed at 160 degrees C and 170 degrees C temperatures for birch and spruce sawdust, respectively. The extraction time was 60 minutes. Three identical extractions were conducted with both sawdust types in the laboratory and the pilot scale. The hemicellulose yields were 50 wt% for birch and 80 wt% for spruce in both the laboratory and pilot scale. Relative standard deviations for hemicellulose yields were <10% between extractions, so the extraction parameters from the laboratory scale setup can be used in the pilot scale extractions.