High resolution infrared absorptivities of chlorine nitrate (ClONO2) are required in order to quantitatively evaluate, by examination of infrared spectra obtained recently from balloon-borne spectrometers, the possible occurrence of this compound in the stratospheres. In the present study, infrared absorptivities for four absorption bands of gaseous ClONO2 have been measured at 0.0625 cm-1 spectral resolution with a Fourier transform infrared (FT-IR) system. Spectra were obtained at two pressures (0.05 and 1.05 torr) of pure ClONO2 and with 125 torr of N2 added to a 0.50 torr sample. Absorptivities for a range of spectral resolutions (0.0625,0.125, 0.25 and 0.50 cm-1) have been calculated from the data.