A group of bifunctional organosulfur compounds were tested as pyrite depressants for improving the separation of coal and pyrite by selective oil agglomeration. Preliminary screening tests of potential depressants were carried out with pyrite which had been sulfurized by treatment with a freshly acidified solution of sodium sulfide to increase its response to oil agglomeration. High-grade mineral pyrite was used for most of these tests, but pyrite extracted from coal was used for some tests. When heptane was used as an agglomerant, the following organic thiols were found to suppress the agglomeration of sulfurized pyrite: thioglycolic acid, thiolactic acid, mercaptosuccinic acid, 3-mercaplopropionic acid, and 2-mercaptoetbanesulfonic acid. Each of these materials contains both a sulfhydryl group (-SH) and a hydrophilic group. The materials were also shown to improve the separation of artificial mixtures of Illinois No. 6 coal and sulfurized pyrite in other tests involving agglomeration with heptane. However, the best separation was achieved when thioglycolic acid was employed.