When managed appropriately, many patients with both Hodgkin's and non-Hodgkin's malignant lymphoma can now be cured. Of major importance in selecting curative therapy is ascertainment of the extent, or stage, of disease. Although the roles of many diagnostic procedures applied in staging are well defined, that of staging laparotomy remains controversial. When the role of staging laparotomy is examined, Hodgkin's and non-Hodgkin's malignant lymphoma must be considered separately. Although the Ann Arbor staging classification is currently used for both diseases, its clinical utility has been established only for Hodgkin's disease. In Hodgkin's disease, therapy for all histologic subtypes (lymphocyte predominance, nodular sclerosis, mixed cellularity, and lymphocyte depletion) depends on knowing whether the patient is stage I, II, III, or IV. In most series, less than 15% of the patients are determined to have stage IV disease prior to laparotomy. Since therapy often changes when patients are found to have stage