A Fourier transform spectrometer aboard an aircraft at 12 km has been used to measure the stratospheric overburden of carbonyl sulfide (OCS). Line parameters derived from laboratory measurements of OCS absorption spectra made with the same instrument were used to interpret the results. Column abundances were determined for winter and summer at latitudes from the equator to 48 ¿N. The mean vertical column abundance above 12 km is 1.9¿1015 molecules-cm-2, corresponding to an average volume mixing ratio of 4.6¿10-10. We observe little variation with latitude or season.