Analysis of the treatment and follow-up records of 377 Hodgkin's disease patients who received mantle irradiation but no planned chemotherapy reveals an overall supradiaphragmatic relapse rate of 21%. Complications of treatment included symptomatic pulmonary radiation reaction (20%), pericarditis (13%), Lhermitte's sign (15%), and thyroid dysfunction (13%). The addition of a subcarinal block after 2500 to 3500 rads and the use of the thin lung block technique in selected patients have reduced the incidence of pulmonary and pericardial complications to less than 5% without sacrificing local control. Further modifications in technique and treatment policy are discussed in terms of improving the therapeutic ratio.