This paper reviews the phenomenology of the mystical experience and its varied contexts epilepsy, toxicity, organic brain syndromes, the major psychoses and hysterical dissociative states as well as in apparently normal persons. The impact of the experience on the personality is noted and its significance briefly reviewed. The author notes that two fallacies await the unwary psychiatrist: the fallacy of reductionism which defines the mystical experience in pathological terms only; and the fallacy of speculation without adequate philosophical or theological tools.