Secondary amyloidosis without a known cause, diagnosed antemortem in a patient with idiopathic myelofibrosis, is reported here. This is the first such case, to our knowledge. Amyloid deposits were seen in the bone marrow, renal glomeruli and jejunum. Reasons for investigating for amyloidosis were hypogammaglobulinemia, proteinuria and recurrent diarrhea. (C) 1997 Elsevier Science Ltd.