Coal-fired combined cycle power generation systems, based on fluidized bed combustion and/or gasification, are being introduced that offer significant advantages over pulverized fuel (pf) firing. Materials selection and performance are key factors in determining the availability of these systems. This paper reports the approach to materials testing adopted for gasifier hot gas path components in British Coal's Topping Cycle Development Programme’and outlines some of the findings. This testing is aimed at generating a database of corrosion and other materials performance data from the exposure of alloys and coatings in gasifier fuel gas environments at a range of temperatures from 300 to 900°C. Detailed characterization of the fuel gas environment has been carried out in an atmospheric gasifier using selected elements and compounds. Activity windows have been defined for sulfur and oxygen in the required temperature ranges and compared with those predicted from calculations based on the fuel gas composition. Materials performance data for four alloys, including 310ss and Haynes HR 160, are also presented. These data illustrate the similarities and differences between results obtained from atmospheric pressure and pressurized conditions, the types of corrosion damage morphologies observed and the effect of changes in gas chemistry on the extent of the damage.