Macroglossia and skeletal muscle enlargement with weakness appeared in a 38-year-old male who was shown to have amyloidosis and light chain multiple myeloma. Free lambda light chains were present in serum and urine. Skeletal muscle contained large amounts of amyloid and other amorphous material infiltrating blood vessel walls and connective tissue. Muscle fibers, particularly the type II variety, were diminished in size. Amyloid and similar amorphous material also were present in skin. This patient represents an unusual, but somewhat uniform, type of involvement of the neuromuscular apparatus in nonfamilial primary amyloidosis.