The IgM myeloma is a rare type of multiple myeloma (MM) with some features which differentiate it from other immunologic types of myeloma and from Waldenström macroglobulinemia (WM). Two patients with IgM myeloma in whom the only clinical feature of the disease was the development of bone lesions and general deterioration are reported. In none of the cases an M component was detected in proteinogram. A bone marrow proliferation of plasma cells was discovered in both, which it was accompanied with dura mater infiltration in one of them. The type of secreted immunoglobulin was IgM lambda in the first case and kappa in the second. Both patients had a poor clinical course after the diagnosis and died due to infective complications. Emphasis is made on the need to differentiate this condition from WM due to their different prognosis and therapy.