Experimental studies are reported on the initiation-deflagration process occurring in nitroglycerin and nitroglycerin solutions as a result of impact. The instrumented apparatus used permitted determination of the pressure/time relationships due to the momentum of the impacting weight and to the resulting deflagration. As a result, impact sensitivity testing of liquids is placed on a sounder basis. A gradual decrease in impact sensitivity is observed as desensitizer concentration is increased up to 16 per cent by weight; a more rapid decrease in sensitivity is found beyond this point.