Introduction In 1944 Waldenström described a clinical syndrome under the title "incipient myelomatosis"1which he subsequently renamed "macroglobulinemia."2S i n c e that time about 200 similar cases were reported principally in the foreign literature. A number of recent reviews3-6have established the following as the outstanding characteristics of the disease. 1. It is a chronic debilitating illness primarily affecting males between the ages of 50 and 80. The usual life expectancy after the first manifestation of symptoms is 2 to 10 years. 2. The onset is insidious, usually characterized by progressive weakness, lassitude, weight loss, and pallor. Edema may be present. 3. Hemorrhagic diathesis is present in at least two-thirds of the cases and is manifested primarily by epistaxis, gingival and retinal hemorrhages, cutaneous p u r p u r a (usually late), and to a lesser extent bleeding from other organs. 4. Painless enlargement