A middle-aged female presented with diffuse planar xanthomas, associated with normal plasma lipids and a severe crescendo angina. Hematological testing disclosed the presence of a cryoglobulin binding to apolipoprotein B. The patient died after a short and dramatic clinical course. At autopsy, a markedly thickened aorta with diffuse atheromatous lesions of the major peripheral arteries were observed. Intracytoplasmic filaments (50-100 A), comparable to those described in amyloid deposits, were also detected. Endothelial cells were filled with lipid-containing vacuoles without extracellular lipid deposits. The reported case indicates that benign gammopathies against 'atherogenic' lipoprotein components, without clinical myeloma, may result in the development of severe arterial lesions.