Instrumentation is described which has been tailor-made for measurements in high-temperature flames. The measuring instruments have been developed and tested in oxy-natural gas flames of thermal input 0.8 to 1 MW. In particular, a high-temperature suction pyrometer has been developed for temperature measurements up to 2400 K. The instrumentation has been used to collect a comprehensive set of in-flame data in oxy-natural gas flames. This includes the determination of CO2, O-2, N-2, CO, H-2, NOx, unburnt hydrocarbons (UHC) and CH4, and the measurement of axial velocity, turbulence, temperature, total radiance profiles and total radiative fluxes at the furnace wall.