The characteristics and physiological accompaniments of the respiratory disorder in the Rett syndrome are reviewed and placed in the context of other clinical studies. Events are indicated which may play a part in the occurrence of vacant spells. A scheme is proposed to explain the various manifestations of the Rett syndrome disorder throughout life. The Rett syndrome is viewed as a developmental disorder in which the evolving clinical signs are due to the effects of maturation and aging on an abnormal brain rather than to primary degenerative disease. Thus development elicits preexisting defects which subsequently become clinically manifest. The clinical evidence is suggestive of a genetically determined early defect in central receptive processing which leads to failure of central motor planning with release of extrapyramidal rhythms.