Ketone peroxides are capable of spontaneous decomposition, and violent decomposition occurs if they contact with strong mineral acids. In this paper, an adiabatic method is used to investigate the thermal hazard of Methyl Ethyl Ketone Peroxide (MEKPO) and mixture of MEKPO with sulfuric acid in order to understand the effect of the contamination of sulfuric acid on the thermal stability of MEKPO. On the basis of experimental results, kinetic parameters of exothermic reaction of MEKPO and mixture of MEKPO with 1% sulfuric acid are estimated, and thermal hazard parameters, such as the initial exothermic temperature and the adiabatic temperature rise are obtained under real adiabatic condition. It can be seen from the results that the thermal hazard of MEKPO with sulfuric acid is more remarkable than that of MEKPO itself. (C) 2003 Elsevier Ltd. All rights reserved.