There has been much neglect in the study of the factors causing malaise and illness resulting from rapid long-distance travel. Transmeridional travel causes a dysrhythmia because internal clock systems have to adjust to unaccustomed rhythms. The nature of neuronal action is described and the clock-like activity of the nervous system is outlined. Disturbances of brain rhythms (e. e. g.) are described. The important factors which influence health before and after flight are emphasised. A plea is made for wider publication of information about the causes and prevention of illness associated with rapid long-distance travel.