The impact reactivity ("the first reaction") of 16 nitramines was determined as the drop energy E-d, required for 50% initiation probability. Relationships have been found between the E-d values, on the one hand, and heats of fusion, N-15 NMR chemical shifts of aza atoms in reaction centers, parameters of low-temperature thermolysis, and oxygen balances of nitramines studied, on the other. Taking these relationships the E-d values were predicted for four nitramines, from which three have not been synthesized yet. On the basis of the said relationships it was stated that the impact reactivity of nitramine molecules depends on the electronic configuration within their reaction centers and on their conformational stability and intensity of their intermolecular interactions. The reaction centers here are the same as in the case of initiation of the nitramines by shock. It is found that epsilon-HNIW possesses higher thermal and impact reactivities in comparing with those of beta-modification.