The exothermic reactions of thermally unstable materials have been studied using self-heating methods in a wire-mesh-reactor as well as temperature-programmed methods utilizing a differential scanning calorimeter (DSC). Samples of lignite coal dust, cork dust, detergent powder and riboflavin (vitamin B2) were investigated. The overall activation energy E could be determined for each method. For lignite coal and cork dust all techniques show very nice agreement in E. For the detergent powder, the values are comparable except for the heat-release (HR) rate method value which is about 50-60 kJ/mol higher. Riboflavin on the other hand shows a different behaviour. The DSC-experiments lead to values being significantly higher compared to the self-heating values. The existing differences are clearly worked out. (C) 2003 Elsevier Ltd. All rights reserved.