The concentration of carbonyl sulfide (OCS) has been determined in several preindustrial air samples extracted from a shallow ice core from Siple Dome, West Antarctica. The extraction of the air was carried out by shredding the core under vacuum, followed by analysis by gas chromatography with mass spectrometric detection. 11 ice core samples were analyzed, ranging in depth from 82.3 to 90.7 m. The ages assigned to OCS in the ice core samples range from 1616 to 1694 AD. The observed OCS mixing ratios range from 322.6 pptv to 442.3 pptv with a mean of 372.8 ¿ 37.2 pptv. These levels are significantly lower than the present day atmospheric mixing ratio of 500 pptv and suggest that the anthropogenic sources comprise approximately 25% of the present day OCS budget.