The risk of Hodgkin's disease following non-Hodgkin's lymphoma (NHL) was estimated using information collected by the National Cancer Institute's Surveillance, Epidemiology, and End Results Program. Histopathologic material representing both diagnoses was reviewed for 11 patients in whom Hodgkin's disease was reported after NHL. Diagnoses of both diseases were confirmed in nine patients. Comparisons with population rates indicated that patients with NHL are at an almost threefold risk of subsequently having Hodgkin's disease. Survival in this series was poor; seven of the nine patients died within 16 months after the diagnosis of Hodgkin's disease.