In biorefineries several conversion processes for biomasses may be applied to obtain maximum value from the feed materials. One viable option is the liquefaction of lignocellulosic feedstocks or residues by fast pyrolysis. The conversion technology requires rapid heating of the biomass particles along with rapid cooling of the hot vapors and aerosols. The main product, bio-oil, is obtained in yields of up to 75 wt% on a dry feed basis, together with by-product char and gas which are used within the process to provide the process heat requirements; there are no waste streams other than flue gas and ash. Bio-oils from fast pyrolysis have a great potential to be used as renewable fuel and/or a source for chemical feedstocks. Existing technical reactor designs are presented together with actual examples. Bio-oil characterization and various options for bio-oil upgrading are discussed based on the potential end-use. Existing and potential utilization alternatives for bio-oils are presented with respect to their use for heat and power generation as well as chemical and material use.