The light chain deposition disease was recently identified as a systemic clinicopathological entity characterized by amorphous extracellular deposits which differ from the amyloid substance. Various organs may be involved, notably the kidney, the liver, the myocardium and the skin. The histopathological aspects were investigated in 3 cases. By immunofluorescence using frozen sections the deposits were shown to contain monoclonal light kappa or lambda chains. By electron microscopy they appeared to be granular and usually located close to epithelial and/or vascular basal lamina. There was in every case a monoclonal lymphoplasmacytoid proliferation. In one case amyloid deposits were associated in small vessels. In another one, follow-up study after chemotherapy showed improvement of hepatomegaly, stabilization of renal function, and regression of light chain deposits in skin biopsy specimens.