Athorough assessment has been made of the characteristics of bio-oil from fast pyrolysis of biomass. Fast pyrolysis uniquely gives high yields of a homogenous mobile liquid for direct use for heat and power and indirect use for biofuels and green chemicals. An improved understanding of the significance of the different aspects of quality of bio-oil helps to establish standards and key quality requirements which help to define limitations for use. An appreciation of the potential for bio-oil to meet a broad spectrum of applications in renewable energy has led to a significantly increased R&D activity in studying the science and technology of fast pyrolysis with increased emphasis on quality improvement. This increased activity is evident in North America, Europe and Asia with many new entrants as well as expansion of existing activities. The only disappointment is the continued limited industrial development and deployment of fast pyrolysis that are necessary to provide the basic bio-oil raw material for the development and exploitation of applications.