Many recent changes in medical area such as expansion of medical insurance, high expectation of people for medical service and the competition with foreign country open new area of medical service and hospital managements. Domestic medical personal have been doing their best for better medical service and more efficient hospital management. In other words, they are focusing on the renovation of organization culture, the reform of organization and operation process and building information systems. It has been more than 10 years since the first computer system was introduced in the domestic medical area. We have been trying to build more advance and more friendly computer systems. Recent advances of information technology could make this possible. In this paper, I introduce the system design of Integrated Hospital Information System include core technology, components of the system and important factors to be considered.