The analysis of exhaust gas is becoming an increasingly important tool in determination of the performance of high temperature combustion systems. Previous methods involving the collection of gas samples in sampling tubes, followed by subsequent laboratory analysis, have been laborious and time consuming. A new on-line gas analysis system has been put into service, which makes a complete analysis every 30 sec directly at the test site. The system involves the use of five process gas chromatographs to measure oxygen, nitrogen, carbon dioxide, carbon monoxide, and hydrogen, plus a hydrocarbon analyzer to determine unburned hydrocarbons. These measurements in conjunction with other operating data permit the calculation of overall combustor performance, as well as identification of local point-by-point conditions at the combustor exit.