The photolysis of 1,3-dithiol-2-one in argon and nitrogen matrices has been studied by FTIR spectroscopy. The matrices were irradiated with full output of medium pressure mercury lamp. The primary photolysis product is trans-dithioglyoxal that has been identified for the first time by infrared spectroscopy. From the two secondary photolysis products one is identified as thiolthioketene on the basis of its known infrared spectra and the second one is tentatively attributed to ethynyl hydrodisulfide. The latter species has not been detected so far. The identification of the unknown photolysis products is based on their theoretical spectra calculated by MP2/6-311++G(3df,3pd) method. (C) 2008 Elsevier B.V. All rights reserved.