A theoreticalP,v,E,Tequation of state has been derived for the secondary explosive TATB. From this it has been found that the pressures generated within TATB and similar secondary explosives, when they are compressed, should be relatively insensitive to temperature changes at constant volume. For TATB this means that the shock Hugoniot of the nonporous material should remain close to the room‐temperature isotherm up to pressures of about 200 kbar.