Amyloidosis should be considered in any patient older than 40 years who has nephrotic syndrome, congestive heart failure (not on an ischemic basis), idiopathic peripheral neuropathy, or unexplained hepatomegaly. When a patient has one of these problems, immunoelectrophoresis and immunofixation of the serum and urine should be done for the detection of a monoclonal light chain. If a monoclonal light chain is found, a diagnosis usually can be established by amyloid stains performed on a bone marrow biopsy specimen or a subcutaneous fat aspirate. The presence or absence of cardiac involvement with amyloid is the most important prognostic factor. Treatment can range from observation to oral chemotherapy to hematopoietic stem cell transplantation. A practical understanding of the mechanisms underlying this disease can lead to prompt diagnosis and early therapeutic intervention.