National Sanatorium Tama Zensho-en (国立療養所多磨全生園) opened in 1909 as the Zensei Hospital. Its name was changed to Tama Zensho-en in 1941.

One of the first five leprosy sanatoria in the country, it treated patients from Tokyo and 11 other provinces in central Japan. Originally the place was surrounded by a deep and wide ditch and a thorny holly fence three metres high, which still stands today as symbolic of the isolation and confinement of the patients. The largest number of residents on record was 1,518 in 1943. Dr. Kensuke Mitsuda worked as the sanatorium’s chief medical officer starting in 1909. In 1914 he became the Director of the sanatorium.

As of December 31, 2015, the number of residents (former patients) was 197 and the average age was 84.4.

Primary and secondary schools existed within the sanatorium for younger patients. All were closed before 1979.

In 2014, a nursery school was opened within Zensho-en premises to accommodate children from neighbouring communities: a symbol of integration.

The National Hansen’s Disease Museum is located within the premises of Tama Zensho-en sanatorium.