The General Adaptation Syndrome is characterized by three stages: Alarm Reaction - Adaptation - Exhaustion. Results of animal experiments and clinical observations indicate that both central nervous and peripheral systemic reactions to acute stress - e.g. noise - can be accentuated by magnesium deficiency and reduced by mild hypermagnesemia, respectively. Concerning long term suboptimal magnesium supply, experimental data indicate that a stage of adaptation might be achieved during a certain period of time, preceded and followed by stages of markedly decreased resistance.U