Comparisons are made between data obtained from a real-time automotive emissions gas analyzer (Nicolet REGA) system based on a Nicolet Fourier transform infrared spectroscopy (FTIR) analyzer, data from a Mattson FTIR-based real-time automotive emissions analyzer (Pierburg REA), and data obtained from classical analytical techniques. Data from both FTIR systems for CO, CO2, and NOx are compared to both integrated-real time and integrated bag results from conventional emissions analysis instrumentation. FTIR formaldehyde data are compared to results obtained by the 2,4-dinitrophenylhydrazine-coated cartridge liquid chromatography technique. FTIR methanol data are compared with data obtained by gas chromatography analysis of samples collected in water impingers. The exhaust emissions from automobiles fueled with a variety of fuel and fuel blends are analyzed. Advantages and disadvantages of each FTIR system are discussed with regard to choice of compound, ease of operation, and analytical flexibility.