Macrosomatognosia and microsomatognosia, in which the entire body or parts of the body are perceived as abnormally large or small, can occur as hypnagogic hallucinations in sane and healthy subjects. A review of the literature and five original observations are presented. The mouth and the hands are anatomic regions which are frequently affected, paralleling the dominance of their representation in the sensory maps of the human brain. The clinical differential diagnosis of the said phenomena includes narcolepsy, epileptic and migraine aura, drug-induced body schema disturbances and basic symptoms of functional psychoses.