Paranoid Reaction (or bouffée délirante) according to the french classification was the basic psychosis of primitive societies. It corresponds to a need of defense of restructuration or restitution according to a pattern of "misconduction" admitted by the cultural environment. Paranoid reaction, in this respect, offers some relative good pronostic as soon as the goal is reached even if the previous personality remains modified. Paranoid reaction may get closer to hysterical crepuscular states. Some symptoms may also evoke schizophrenias. Evolution toward a lasting psychosis may be considered only in case the process of deculturation/acculturation is already engaged in an irreversible way and the defensive mode presented in the new cultural system shows schizophrenic patterns. Quick transformations and strong cultural pressures, trough that primitive societies are going, might increase dramatically chronic evolution of paranoid reactions. A case has been related to illustrate those considerations.