The pressure-broadening effects of one atmosphere of air or of carbon dioxide on various infrared bonds of hydrocarbons have been measured and compared with the intensity data obtained without pressure-broadening. Measurements have been made on the following hydrocarbons at partial pressures between 0.5 and 20 millimeters and at the following wavelengths: ethylene, 10.52 microns; acetylene, 3.1, 7.4 and 13.7 microns; propylene, 10.95 microns; butene-1, 10.85 microns; trans-2-butene, 10.375 microns; and benzene, 9.50 microns. The variation of optical absorbance at several of the infrared absorption maxima of ethylene and acetylene have been investigated using varying partial pressures of air or carbon dioxide at fixed partial pressures of the two hydrocarbons. (Author)