[en] A two-day workshop on the accelerator for particle therapy was held on August 22-23, 1990, with the aim of mutual understanding of medical accelerators among investigators. The state-of-the-art facilities in Japan and medical proton accelerators in Japan and other countries were introduced. This is a compilation of papers presented at the workshop: (1) particle radiotherapy at the National Institute of Radiological Sciences (NIRS); (2) proton therapy; (3) treatment planning, especially for photon and electron therapies; (4) heavy ion synchrotron project at the NIRS; (5) medical proton accelerator project of Tsukuba University and recent status of Loma Linda University Medical Center Proton Beam Facility; (6) inspection report on the Loma Linda University Medical Center Proton Beam Facility; (7) accelerator project of Kyoto University; (8) actual conditions of the 7 MeV proton linear accelerator; (9) design study of superconducting compact cyclotron prototype model; (10) medical superconducting prototype cyclotron; (11) RCNP cyclotron cascade project; (12) beam extraction from synchrotron; (13) radiation safety design in high energy particle accelerator facilities. (N.K.)