[en] Investigations in proton beam therapy of cancer patients have been initiated at the Cyclotron Laboratory, Harvard University, Cambridge, USA, since 1974 using a proton beam the energy of 180 MeV for fractionated irradition of uveal melanoma (899 cases), chordoma and chondrosarcoma of the base of the skull (96), sarcoma of the soft tissues and bones (79), prostatic cancer, head and neck tumors, etc. (altogether 1331 patients had been irradiated by June, 1986). Proton beam therapy is used alone or in combination with proton beam irradiation, routine radiotherapy. Areas of particular interset are ocular melanoma, chordoma and chondrosarcoma of the base of the skull, paraspinal sarcomas. Investigations in the field of proton beam therapy of malignant meningioma, metastases to the paraaortic lymph nodes hold promise