Pyrolysis of biomass followed by hydroprocessing may provide infrastructure-compatible transportation fuels. In this work, a life cycle assessment (LCA) of the production of gasoline and diesel from forest residues via fast pyrolysis and hydroprocessing, from production of the feedstock to end use of the fuel in a vehicle, is performed. The fast pyrolysis and subsequent hydrotreating and hydrocracking processes are based on a Pacific Northwest National Laboratory design report. Stages other than biofuels conversion, including forest residue production and harvesting, preprocessing, feedstock transportation, fuel distribution, and vehicle operation, are based on previous work. Probability distribution functions are assumed for parameters involved in the pyrolysis process for Monte Carlo uncertainty analysis. This LCA for the production of gasoline and diesel via pyrolysis and upgrading assumes grid electricity is used and supplemental natural gas is supplied to the hydrogen plant. Gasoline and diesel produced via pyrolysis are estimated to have greenhouse gas (GHG) emissions of CO2 equivalent of 117 g km(-1) and 98 g km(-1), respectively, and net energy value (NEV) of 1.09 MJ km(-1) and 0.92 MJ km(-1), respectively. All values from the uncertainty analysis have lower GHG emissions and higher NEV than conventional gasoline in 2005. Grid electricity and natural gas used account for 81% of the net GHG emissions in the base case. An evaluation of a case with biomass-derived electricity shows significant improvement in GHG emissions. (c) 2012 Published by Elsevier Ltd.