Six non-H/sub 2/S sulfur species were identified and quantitated from two different retorting processes, a modified in situ process and an aboveground process. Carbonyl sulfide (COS), methyl mercaptan (CH/sub 3/SH), carbon disulfide (CS/sub 2/), thiophene, methylthiophene, and sulfur dioxide (SO/sub 2/) were determined by gas chromatography combined with a flame photometric detector. One of the in situ retorts produced the highest concentrations of sulfur species while the aboveground retort produced the least of the three retorts studied. However, other modified in situ retorts have been reported to produce relatively low concentrations of sulfur species. Variability in the quantitative data was attributed to variability both in sulfur content of the raw oil shales and in retort conditions. Possible reaction mechanisms were considered. The non-H/sub 2/S sulfur species comprise 0.4-6% of the low molecular weight sulfur species measured in the retort off-gases. Abatement strategies must consider the presence of these trace species if the air quality standards proposed by Colorado are to be maintained.