Since 1969, 184 previously untreated and evaluable adult patients with Hodgkin's disease, staged as I (43) or II (141), have been treated. Eighty patients were part of the National Hodgkin's Disease Study, randomly assigned to receive radiotherapy to either an involved (39) or extended field (41). In a subsequent single-arm study, 104 patients were treated with involved-field radiotherapy preceded and followed by three cycles of MOPP chemotherapy. Median durations of follow-up have been 172, 172, and 92 months, for the involved-field radiotherapy, extended-field radiotherapy, and MOPP plus involved-field radiotherapy treatment groups, respectively. Although significant differences among the three treatment groups were observed with respect to disease-free survival (p less than 0.001), only the group of patients treated with involved-field radiotherapy had a statistically significant decline in overall survival as compared with the two other treatment groups (p less than 0.001). Moreover, patients who underwent clinical staging and were treated with MOPP plus involved-field radiotherapy had significantly prolonged disease-free survival compared with those who underwent surgical staging and were treated with extended-field radiotherapy (p less than 0.001). One of the patients who received MOPP plus involved-field radiotherapy had subsequent development of acute monocytic leukemia, and another had refractory anemia with excess blasts. One instance of diffuse poorly differentiated lymphocytic lymphoma was also observed. Acute monocytic leukemia developed in another patient treated with involved-field radiotherapy. The rates of amenorrhea in the group treated with MOPP plus involved-field radio-therapy were 9.6 percent and 78.5 percent for female patients younger and older than 30 years of age, respectively. Despite the universal azoospermia ensuing after MOPP plus involved-field radiotherapy, in three patients whose sperm counts were checked sequentially for 26 to 53 months after treatment, evidence of spermatogenesis was observed. Three patients with remission of Hodgkin's disease after involved-field (two) and extended-field (one) radiotherapy died from cardiovascular disease that could only be attributed to the prior radiotherapy. Although further follow-up evaluation will be required to determine the impact of the three different treatment modalities on survival and long-term toxicity, MOPP plus involved-field radiotherapy appears to be superior to involved-field or extended-field radiotherapy alone in achieving prolonged disease-free survival without significant leukemogenic potential.