The major objectives of ningen dock, or multiphasic health testing and services, have been moving from secondary prevention to primary prevention. The main reason for this is that recently the majority of the diseases involved have been chronic diseases which develop slowly and without visible symptoms--often the patient is unaware of the fact that he has a disease until the disease reaches an advanced stage. Of course such diseases, since they exhibit few or no symptoms, are hard to detect. Secondary preventive care becomes difficult in such a situation, and primary preventive care is even more difficult. The major diseases of this type at present are neoplastic and arteriosclerotic diseases. Secondary prevention, leading to early detection, has proved more effective in treating cases of neoplastic diseases, while primary prevention, with its consequent reduction of risk factors, has proved to be more useful in dealing with arteriosclerotic diseases. It is therefore highly recommended that computers installed for health testing be utilized for evaluating risk factors and presenting the results to the examinees through colour displays and other devices such as primary care instructions for them. It is relatively easy now to collect time series data and store them in computers. For people who have no symptoms or complaints, a combination of personal and group instructional methods is necessary for carrying out primary care health instructions.