An interlibrary loan system in Japan was established by the Japanese Medical Library Association in 1927. Since then the members of the Association have increased from five to forty-eight—all forty-six medical school libraries and two dental school libraries. The Association's service has been enlarged, particularly since World War II. The number of interlibrary loans among member libraries has increased greatly, especially since 1954, thanks to the development of union lists and photoduplication service. Today, more than 80 percent of the requests are filled with photocopied materials. On the other hand, the growth of medical literature has made interlibrary cooperation very necessary, especially internationally. An agreement was made in 1948 concerning photoduplication service between the Japanese Medical Library Association and the National Library of Medicine.