An 81-year old man who had a plasmacytoma of the ileum presented with melena for which no bleeding site could be established before surgery. He developed intussusception and the tumor was located at laparotomy. Metastases to the skin and axillary lymph nodes were documented prior to his operation, to mesenteric lymph nodes at surgery and to intrathoracic lymph nodes and a substernal goiter at autopsy. The liver, spleen, bones and marrow were not involved by myeloma or amyloid. Immunoelectrophoresis demonstrated an Ig-A (lambda) monoclonal protein in the serum (with nondiagnostic serum zone electrophoresis patterns) and lambda light chains in the urine. Immunoflourescense of Ig-A (lambda) globulin was present in imprint preparations from the bowel tumor.