Prognostic factors for 53 previously untreated patients with Stage IV Hodgkin's disease were analyzed for their effects upon complete remission rate, survival, and disease-free survival following treatment with mechlorethamine, Oncovin (vincristine), procarbazine, and prednisone (MOPP) or MOPP plus bleomycin (MOPP-Bleo). Although 75% of those patients with only one site of extranodal disease achieved complete remission, only 25% of those with more than one site of involvement entered complete remission. Seven of the eight patients with more than one extranodal site were dead of disease at 4 years, compared with a 5-year survival of 75% for those with only one site of involvement. Disease-free survival from complete remission was dependent upon the percentage of planned doses of nitrogen mustard actually administered. Patients who received higher doses of nitrogen mustard had significantly longer freedom from relapse and survival after attaining complete remission than those who received reduced doses. Age, symptoms, pathologic features, and presence or size of mediastinal disease did not affect the couple remission rate, survival, or disease-free survival. Patients with Stage IV disease treated with MOPP alone should receive the highest tolerable dose of nitrogen mustard early in their treatment, since those receiving lower doses have a higher risk of relapse.