The paper discusses on-line measurement of nitrous oxide (N2O) from combustion sources by automated gas chromatography. Fossil fuel combustion is suspected of contributing to measured increases in the ambient concentrations of N2O. Characterization of N2O emissions from fossil fuel combustion and associated pollution control systems has been hindered by the generation of N2O from nitrogen oxides, sulfur dioxide, and moisture present in the sample vessel while samples await analysis. To truly assess N2O emissions from fossil fuel combustion, a real-time or near real-time measurement technique is required. To accomplish this, a gas chromatograph equipped with an electron capture detector was configured and automated. The system is capable of detection levels below ambient concentrations and a practical quantifying range of 0.1 to 200 ppm. A precolumn backflushing system negates the effects of interferents present in fossil fuel combustion emissions. The automated system, capable of one on-line measurement every 8 minutes, has been used to evaluate N2O emissions from a variety of combustion sources, fuels, and post-combustion pollution control techniques.