The effects of the main operation variables (temperature, pressure and gasifying agent composition) on gas production and other process parameters, such as carbon conversion, cold gas efficiency and high heating value, during the steam-oxygen gasification of a bituminous coal were studied. It was observed that temperature and oxygen concentration were the most influential variables during the gasification process. In addition, co-gasification tests of binary blends of a bituminous coal with different types of biomass (up to 10%) and petroleum coke (up to 60%), as well as ternary blends of coal-petcoke-biomass (45-45-10%) were conducted in order to study the effect of blending on gas production and carbon conversion. (C) 2009 Elsevier B.V. All rights reserved.