By means of non-isothermal DTA in its simple form the initial exotherm temperaturesTDof 2,4-dinitrotoluene, 2,6-dinitrotoluene, 2,4,6-trinitrotoluene, 1,5-dinitronaphtalene, 1,8-dinitronaphthalene and 1,4,5,8-tetranitronaphthalene have been determined. By application of the Piloyan method to these measurements, the activation energiesEarising from the decompositions of these compounds were established. The results are discussed from the point of view of the molecular structures of the polynitro compounds.