Systemic amyloid light chain (AL) amyloidosis is a rare protein deposition disease caused by a clonal B cell disorder of the bone marrow. The underlying diseases can be plasma cell disorders (monoclonal gammopathy of clinical significance, smoldering or symptomatic myeloma) or B cell non-Hodgkin’s lymphoma (e.g., Waldenstrom’s disease or marginal zone lymphoma) with secretory activity. It is crucial to characterize the underlying disease very precisely as the treatment of AL amyloidosis is directed against the (often small) B cell clone. Finally, the detection of cytogenetic aberrations of the plasma cell clone will likely play an important role for choosing an effective drug in the near future.