The present research shows how mild oxidation of coal mostly affects the evolution of H2S produced in the reaction of coal with elemental sulphur. Coal samples oxidized at 30, 50, 80 and 150degreesC were reacted with sulphur in a temperature-programmed reactor. The H,S produced in the reaction is very sensitive to the initial stage of the oxidation of coal. The strongest reduction in the amount of H2S evolved was observed in the samples oxidized at 30degreesC. This temperature is lower than the one found in most coal storage places. The reaction with elemental sulphur could be used to monitor the initial stages of coal oxidation, which otherwise would be difficult to follow by conventional analytical methods.