The catalytic conversion of fast pyrolysis bio-oil to hydrocarbon fuels was studied over HZSM-5 at atmospheric pressure. Experiments were conducted in a dual reactor system having two reactors in series. The temperatures in these reactors were in the range 340-400-degrees-C (first reactor) and 350 450-degrees-C (second reactor). The bio-oil was co-processed with tetralin in all the runs. The objective was to maximize the organic distillate product with a high concentration of aromatic hydrocarbons. The maximum amount of organic distillate in the effluent from the second reactor was 21 wt% of the bio-oil feed and the highest concentration of aromatic hydrocarbons was 76wt% of the distillate. The dual reactor system was particularly beneficial when the temperature in the first reactor was low. Thus, with the first reactor at 340-degrees-C, the yields of organic distillate and aromatic hydrocarbons were 15-16 wt% and 8-11 wt% of wood, respectively, which are nearly two-fold compared to those from a single reactor system operated at 340-degrees-C (7.8 wt% and 4.8 wt%). Under the above conditions, the coke plus char yields were 25 26 wt% of wood which are up to 10 wt% lower than from the single reactor system at 340-degrees-C (29 wt%).