The definition of terrorist phenomenon presents several diffuculties given the characteristics of that phenomenon have changed in the course of history and in realation to place. The two principal categories tha thave historically assumed this behaviour tend to consider it both as a destabilization technique used tyically by élits who connect it to some political utopia. The most recent debate has concentrated primarly on the second category as it is the most difficult to classify and, since the Cold War, poses the most delicate international problems.