Increasing growth of communication industries and informatics, cause the world is facing with a new revolution. Revolution of information and communication technologies in all sectors of the economy, society, politic and security of countries has left a significant effect. One of the most important application areas of information technology is the field of health and treatment. Hospital information system is the first and most important system of health care delivery. Hospital information systems are the computer systems that are easy to manage medicine and hospital management information and are designed to improve health care. Investigations have shown that using a hospital information system caused to improve quality of health care and increase satisfaction of clients. Some problems of the health care system are distribution of patients’ information and Lack of access to their records, Weak cooperation between physicians and health care workers, and also weakness of access to necessary medical information. These problems are solvable through the development of information technology and especially hospital (Health) information systems. This paper studies the hospital information systems, implementation of these systems and their role in the development of medical and health services.