A total of 57 patients with Hodgkin's disease limited to above the diaphragm (Stages I and II, A and B) were treated with radiation therapy alone at the University of Florida between 1964 and 1974. Staging laparotomy was done on 24 patients (42%). A total of 16 patients have relapsed, 4 within the treatment fields, 3 marginally, and 9 as extensions. Analysis of dose vs. size showed no in-field failure with disease less than 6 cm in size, with a range of doses. Massive disease continued to recur occasionally, even with higher doses. Most of the massive disease was mediastinal or hilar; the risk of lung or pleural involvement as determined by x-ray and/or biopsy showed a dramatic increase with size of mediastinal/hilar disease. Only 2 (5%) of 43 patients with mediastinal disease less than 6 cm in size had lung or pleural involvement, compared with 10 (71%) of 14 patients with disease greater than 6 cm in size. Both in-field recurrence and generalized relapse were closely related to the number of anatomical sites involved. Treatment programs need to consider tumor size, particularly in the mediastinum, and the number of sites involved.