The commercialization of biomass-derived pyrolysis liquids for use in heat and power applications is dependent on the ability to successfully provide a fuel of acceptable quality to an end user at a competitive price. One of the intentions of the European Union (EU) Altener 4.1030/C/00-015/2000 project was to derive standards for biomass-derived pyrolysis liquids, based on a consensus between providers of the equipment (boilers, engines, and turbines) and the producers of the liquids. Five basic properties (homogeneity, water content, solids content, stability, flash point) for the liquids are used as the primary criteria for pyrolysis liquid evaluation. Specific values are proposed to ensure that pyrolysis liquids meet a minimum grade that is acceptable for use as a fuel oil in boilers and engines. Data on emissions from boilers, engines and turbines are presented. Preliminary long-duration test data from boiler use are available to allow more- detailed specifications on secondary properties to be made. The purpose of this work is to ensure that a realistic set of specifications is determined, to allow the introduction of pyrolysis liquids into existing fuel infrastructures and markets.