Two women with lymphoplasmocytoid immunocytoma (Waldenström's macroglobulinaemia) have been followed up, one for 23 years and the other for 18. In the first patient the disease presented at the age of 40 years with lassitude and paraesthesiae. Investigation revealed monoclonal IgM-lambda with a serum IgM of 3350 mg/dl and marrow infiltration by lymphoplasmocytoid cells. As there were no symptoms, apart from migraine attacks which responded well to plasmapherese, and because haemopoiesis was unaffected and the lymph nodes were not enlarged, no cytostatic has so far been given. The proportion of lymphoplasmoid cells in the marrow is at present 50%. In the second patient the disease presented at the age of 33 with involvement of stomach and lung, and a conglomerate tumour in the upper abdomen. The serum showed an M-gradient together with raised IgM (3056 mg/dl). Chemotherapy (COPP protocol) and local irradiation of the stomach achieved full remission. At intervals of several years there have been histologically confirmed recurrences in the hypophyarynx, ovaries, hilum of left lung and, most recently, in the upper abdomen once more. These have been successfully treated by resection and local radiotherapy (hypopharynx), operation followed by chemotherapy (COP protocol) (ovaries, upper abdomen) or by radiotherapy alone (hilum of lung-50 Gy).