The association between chronic urticaria, macroglobulinaemia and various other manifestations has been individualized as Schnitzler's syndrome. We report the terminal course of an original case followed up for 20 years, which ended as lymphoplasmocytic lymphoma with multiple sites, whereas no lymphomatous proliferation, meticulously looked for, had never been found hitherto. The lymphoma, associated with a macroglobulinaemia level above 5 milligrams, was diagnosed as Waldenström disease. Although most cases of Schnitzler's syndrome seem to follow a benign course (but the follow-up is not always long) a few cases have been reported showing evolution towards, or association with, lymphoma. This indicates that the follow-up of patients with Schnitzler's syndrome should be prolonged.