Condensed phase and gas phase combustion emissions were monitored from an enclosed, axi-symmetric natural gas/toluene flame with gas chromatography/mass spectrometry, on-line mass spectrometry, and tunable diode laser absorption spectroscopy. The system was operated at global equivalence ratios (GER) from fuel-lean to fuel-rich. Toluene concentrations were monitored with the mass spectrometer, and used for the determination of destruction and ,removal efficiency (DRE) as a function of GER. The condensed phase data indicated that increases in the emissions of toxic compounds, such as polynuclear aromatic hydrocarbons, coincided with decreases in DRE. Products of incomplete combustion, carbon monoxide, methane, and acetylene were measured with tunable diode laser absorption spectroscopy and the results indicate that acetylene was a sensitive surrogate for both DRE and toxic emissions from the combustor.