Œsophageal cancer may be classified into pharyngoœsophageal, mid-œsophageal, and cardio-œsophageal tumours. Teleradium therapy, intracavitary treatment by radium bougie, or implantation of radon seeds are the principal radium treatment methods available.Teleradium therapy is recommended for the pharyngoœsophageal group, and suggestions are offered as to its advantages over X-ray therapy. Mid-œsophageal tumours may be treated by radium bougie or radon seed implantation. The radium bougie technique employed at the Royal Cancer Hospital is described in detail. Radon seed implantation is recommended only as a palliative procedure, and Negus's method of implantation is briefly described.Radon seed implantation is recommended as a purely palliative procedure for cardio-œsophageal neoplasms, and the technique employed at the Royal Cancer Hospital is described.The results obtained in the treatment of sixty-eight cases of œsophageal cancer are given in tabular form.A detailed account of the investigation of the physical conditions of the treatment techniques employed, including integral dose calculations, is given.