Subsequent monoclonal gammopathies

21 patients with 'subsequent' monoclonal gammopathies which developed after non-tumour or tumour states were studied. The cases were selected from 221 patients producing M protein, partly based on retrospective analysis and partly on data of case history, autopsy, histology, and immunochemistry obtained during continuous observation. Possible ways of development of immunoglobulin-producing monoclonal cell clones are also discussed.