Before going into detailed consideration of the various factors relating man to his work it is necessary to understand the part played by the man himself. In any activity a man receives and processes information, and then acts upon it. The first of these, the receptor function, occurs largely through the sense organs of the eyes and the ears, but information may also be conveyed through the sense of smell, through touch, through sensations of heat or cold, or through kinaesthesia. This information is conveyed through the nervous system to the central mechanism of the brain and spinal cord, where the information is processed to arrive at a decision. This processing may involve the integration of the information being received with information which has already been stored in the brain, and decisions may vary from responses which are automatic to those which involve a high degree of reasoning or logic. Having received the information and processed it, the individual will then take action as a result of the decision and this he will do through his effector mechanism, usually involving muscular activity based on the skeletal framework of the body. Where an individual’s activity involves the operation of a piece of equipment he will often form part of a closed loop servo-system displaying many of the feedback characteristics of such a system. Moreover he will usually form that part of the system which makes decisions and it will therefore be appreciated that he has a fundamental part to play in the efficiency of the system. To achieve maximum efficiency a man-machine system must be designed as a whole, with the man being complementary to the machine and the machine being complementary to the abilities of the man. To understand how these processes function it is desirable to know something of the nervous system, of the functioning and capacity of the central mechanism, of the structure of the body, the bones and the joints, and of the muscles which provide the motive power. Additionally, something needs to be known of the source of the power which drives this mechanism, and of the limits of the output which can be expected from it. These activities are not of course carried out in vacuo. An individual may be working in an environment which is too cold, just right or too hot. He may be subjected to such extremes of heat that his mechanism for regulating the body temperature may be in danger of breaking down unless he moves to a cooler environment. He may be subjected to noise which may be of such intensity and duration that he may suffer physical impairment of hearing. He has to be in communication with others; this may take the form of drawings, of written instructions or may be verbal. If it is the latter, noise may be an interfering factor. To be able to see he must have light, which should be of a quality and quantity adequate to the needs of the job. His performance may even be affected by the colour of his surroundings. His work must be organized so that he can maintain his maximum efficiency and interest and so that his abilities are being fully utilized. His relationships with other members of his working group should be such that his efficiency is not interfered with. These factors are illustrated in Fig. I. These are the important ingredients of successful work design, and anyone who sets out to study a particular work situation should take them all into consideration.