This article reviews the clinical manifestations, diagnostic criteria, and treatment strategies for the acute leukemias, the myelodysplastic syndrome, Hodgkin's disease, and the non-Hodgkin's lymphomas in the elderly. These are relatively common diseases in the elderly, and age is traditionally thought to be a bad prognostic sign. The treatment of these diseases is more difficult in the elderly, but careful attention to concomitant underlying illness and general physical condition and the natural history of the diseases can result in very successful management of otherwise lethal disorders.