Two patients are presented with lymphadenopathy, hepatosplenomegaly and infiltration of the bone marrow with plasmocytoid cells in whom an important heterogeneous hyperimmunoglobulinemia was detected (3.18 and 5.85 g/ 100/ml). Autopsy showed widespread poorly differentiated lymphocytic lymphoma with plasmocytoid differentiation in the first case and a well differentiated lymphocytic lymphoma with plasmocytoid differentiation involving lymph nodes, marrow, spleen, liver and kidney in the second case. High concentrations of IgM and IgG were detected in lymph node and spleen homogenates from this case. After splenectomy and cyclophosphamide the immunoglobulins decreased. It is suggested that both cases had a malignant lymphoma with plasmocytoid differentiation and polyclonal gammopathy.