A multi-component, quantitative FTIR spectrometric method has been developed for the simultaneous determination of the concentrations of acetaldehyde, HCN, NO, and CO present in gas phase cigarette smoke. A 50 cc portion of gas phase cigarette smoke from a five port smoking machine is trapped in a sample loop, diluted with nitrogen, and transferred to a simple transmission gas cell positioned in the sample compartment of a table-top FTIR spectrometer. Thirty seconds of the standard one minute smoking cycle are used to collect an infrared spectrum. The remainder of the time period between puffs is used to flush the gas cell with nitrogen. The infrared spectrum contains absorption lines specific for each of the analyte gases. Calibration curves were obtained by relating selected absorption peak areas to known concentrations of the individual gases. The spectral response of an FTIR spectrometer is stable and frequent calibration is not required. The wavelength accuracy of an FTIR spectrometer permits automated and reproducible measurement of absorption peak areas. A micro-computer is used to control the flow of smoke and purge gas through the gas cell, and to analyze the spectral data. The entire analysis procedure is designed for simple and reliable operation. The FTIR spectrometer replaces, and provides comparable results to, individual instruments currently used for the analysis of each gas.