The industrial medical officer, in addition to his duties in organizing and supervising first-aid services for the treatment of injuries incurred in factories and other industrial establishments, is often able to play an important part in limiting or preventing the accidents responsible for these injuries. His scope of action is normally an in direct one, dependent on advice to the management about the conditions of work in the factory and on the personal qualities of the workers, but we shall see that it may be of considerably greater importance than anything that can be effected by mechanical improvements such as the better safeguarding of moving machinery. This side of accident pre vention is the province of the engineer and does not concern the medical officer, but many of the duties commonly assigned to ' safety ' engineers relate to the psychology of the workers and should therefore be of interest to the medical officer. Before describing the influence of various con ditions on accident causation it will be well to quote some statistical information about the frequency of accidents of various types, for it is only in this way that we shall be able to grasp the magnitude of the problem. For the information adduced we are chiefly indebted to the invaluable data published every year in the Reports of the Chief Inspector of Factories.