The authors conducted a study designed to evaluate the hypothesis that irradiation to the heart in the treatment for Hodgkin's disease (HD) is associated with increased coronary heart disease (CHD) mortality. This report describes 957 patients diagnosed with HD in 1942-75 and analyzes follow-up findings through December 1977. Twenty-five coronary heart disease deaths have been observed, and 4258.2 person-years of experience at risk have been accrued. The relative death rate (RDR), defined as the CHD mortality for heart-irradiated subjects divided by the mortality for nonirradiated subjects, was estimated. After adjustment for the effect of interval of observation, age, stage, and class, the RDR estimate is 1.5 but does not differ significantly from unit (95% confidence limits: 0.59, 3.7).