The Problem-Oriented Medical Record (POMR) system was proposed as a new method for the writing of records by Dr. Lawrence L. Weed in 1969. This method is characterized not only by a new manner of writing medical records but also by a new concept of medical practice for patient-oriented medicine. Because of this concept of patient-oriented clinical practice, it has spread rapidly throughout the world. The two medical doctors who independently introduced the PO system in Japan in 1972 are mentioned in this report. This report describes the historical background of the PO system in the United States and how an entry is made in medical records according to the PO system in our country.