An ESZ KTTV instrument of a new, relatively simple construction has been applied to determination of electric spark sensitivity of 29 polynitro arenes, expressed as spark energy, EES, required for 50-percent initiation probability. The thermal stability thresholds, Tmax, were calculated from the published Arrhenius parameters of monomolecular thermal decomposition of the studied compounds, predominantly obtained under the conditions of the Russian manometric method. An approximate relationship has been found between the ln EES values and threshold Tmax values. In the sense of this relationship, the compounds studied fall into several sub-groups. The reason of the said diversification lies in the decomposition reaction rate at the temperature of onset of their thermal decomposition. It has been found that in each sub-group increasing thermal stability of polynitro arenes is accompanied by increasing electric spark sensitivity of these substances. This fact must be taken into account if we deal with the problem of electric spark energy transfer into the reaction centre of the molecule.