A total of 590 patients with Stage IA-IIIB Hodgkin's disease received mantle irradiation at the Joint Center for Radiation Therapy between April 1969 and December 1984 as part of their initial treatment. Recurrence patterns as well as pulmonary, cardiac and thyroid complications were analyzed. Pulmonary recurrence was more frequently seen in patients with large mediastinal adenopathy (LMA); 11% of patients with LMA recurred in the lung in contrast to 3.1% with small or no mediastinal disease, p = 0.003. Hilar involvement, when corrected for size of mediastinal involvement, was not predictive of lung relapse. Patients with LMA also had a high rate of nodal relapse above the diaphragm (40%) following radiation therapy (RT) alone as compared to similarly treated patients with small or no mediastinal adenopathy (6.5%), p less than 0.0001. This risk of nodal recurrence was greatly reduced (4.7%) for LMA patients receiving combined radiation therapy and chemotherapy (CMT), p less than 0.0001. Sixty-seven patients (11%) with hilar or large mediastinal involvement received prophylactic, low dose, whole lung irradiation. No decrease in the frequency of lung recurrence was seen with the use of whole lung irradiation. Radiation pneumonitis was seen in 3% of patients receiving radiation therapy alone. In contrast, the use of whole lung irradiation was associated with a 15% risk of pneumonitis, p = 0.006. The risk of pneumonitis was also significantly increased with the use of chemotherapy (11%), p = 0.0001. Cardiac complications were uncommon with pericarditis being the most common complication (2.2%). Thyroid dysfunction was seen in 25% of patients and appeared to be age-related. These data suggest that the long-term complications of mantle irradiation are uncommon with the use of modern radiotherapeutic techniques. The use of prophylactic whole lung irradiation is no longer recommended since its use did not reduce pulmonary relapse but did increase the risk of pneumonitis. Chemotherapy is also associated with an increased risk of pneumonitis, however, its use in patients with large mediastinal adenopathy appears justified.