The reaction of,gas-phase conversion of dimethyl disulfide and diethyl disulfide in the presence of solid catalysts in different environments at atmospheric pressure and a temperature of 200-350 degreesC was investigated. Over catalysts that contain Bronsted and Lewis acid sites on their surface, the disulfides decompose in a helium atmosphere to yield thiols by eliminating H2S and ethylene; the reactions proceed via independent routes. A produced thiol disproportionates to for rn the sulfide and H2S, this process is retarded in the presence of water. The addition of H2S to helium increases the reaction rate. The yield of thiol in terms of the disulfide converted is 60-87 mol % at 90% disulfide conversion over catalysts containing weak Lewis acid sites, but increases to 92-98% over hydrogenating sulfide catalysts at t = 200 degreesC in a hydrogen atmosphere.