The spark energy, E_ES, required for 50 percent initiation probability of 41 polynitro compounds was determined. The relationships between the E_ES values and impact sensitivity, expressed as drop energies E_d of the "first reaction", were established and discussed. The conclusion is made that depending on intermolecular interaction factors in crystals of energetic materials, the mechanism of impact energy transition to the reaction centre of their molecule can be differ from that of transition of energy of electric spark.