Biomass pyrolysis oils (biooils) are usually unstable when stored for long periods of time especially at ambient conditions and higher temperatures.  The viscosity of biooil tends to increase with storage time because of continuing chemical reactions.  We have developed fractional catalytic pyrolysis process for producing stable biomass pyrolysis oils.  Biooils produced using this method had very low viscosities  that did not increase after one year of storage at ambient conditions. The biooils produced by this method were distilled and fractionated using conventional petroleum processing technologies without forming any char residues.  The biooil had very low ash, alkali, and alkaline earth metals contents and therefore more suitable for a wide range of applications.  The biooil could be potentially use for heating fuel, upgraded to diesel fuels, use for production of phenolic resins and adhesives and many other products.