Statistics and an excellent review of the literature are presented to show that 'accident proneness' is a definite nosological entity. The attempts of Dunbar and others to explain this proneness on the basis of a traumatophilic diathesis has led to some strongly suggestive results. Accident-prone individuals tend to respond to stimuli by action rather than by thought and brooding; they are always in a hurry and they love powerful machinery. They try to avoid compulsion both in the form of authority and in the form of responsibility.