A new sensor system has been developed which is based on UV emission spectroscopy in combination with tomographic evaluation procedures. It has been tested in several combustion systems for temperature determination and for monitoring selected flame radicals as early indicators of NOx production. Flame radicals are identified and monitored using molecular UV emission bands while temperature is measured via blackbody radiation from soot, coal and dust particles within the same spectral region. A strong correlation was found between high temperature/high NOx flue gas emissions and high NH/CN band emissions in an incinerator and between high NO2 flue gas and high CN band emission in a coal-powder-fired power station combustor. In a 1-MW brown-coal fired combustor tomographic measurements were tested using two sensors in a fan beam configuration. The radial temperature calculated perpendicular to the connection line between the sensors was found in good agreement with suction thermocouple measurements. Firing the same burner with propane fuel the two-dimensional distributions of CH, OH, CN and C-2 could be detected.