An inventory of the acute and late reactions to radiotherapy in the treatment of Hodgkin's disease was done. Some of these reactions are trivial and others may be extremely serious and debilitating, varying with the part of the body irradiated. Most of the acute reactions are transient, as are most of the subacute ones. A few of the late reactions are permanent and only a very small number are debilitating. For the most part, the treatment of acute and subacute reactions is symptomatic, and the treatment of late reactions is almost nonexistent, which points up the necessity for extreme care in the delivery of curative radiotherapy. Above all, understanding that the great part of the reactions will disappear and are of little consequence can be most reassuring to the patient and his attending physicians.