The effect of hydrogen sulfide on organic sulfur behavior has been investigated for subbituminous and bituminous coals during heat treatments in free-fall and fixed-bed reactors. The organic sulfur content in the solid phase was observed to increase, even with the rapid release of volatiles. The change in the amount of sulfur and its rate of increase were found to be approximately inversely related to the carbon content of the raw coal and volatile matter release rates. Increases in sulfide and thiophene forms were identified by sulfur K-edge X-ray absorption near-edge structure analysis for the hydrogen sulfide-adsorbed chars. Langmuir's adsorption isotherm was found to characterize the effects of hydrogen sulfide concentration on the uptake behavior of sulfur by rapid pyrolysis chars in nitrogen streams containing hydrogen sulfide at 1073 K in a fixed bed. Gasification of the hydrogen sulfide-adsorbed char showed a lower conversion of sulfur from the solid phase to the gaseous products compared to the loss of carbonaceous substances from the gasified chars.