The authors report electron microscopic findings in brain, bone marrow and liver biopsies in a case of juvenile Niemann-Pick disease (Crocker's type C). The diagnosis was supported by clinical data increase of blood sphingomyelin and vacuolated histiocytes in bone marrow and liver. Neurons and glial cells were filled with two types of cytosomes: classical multilamellar bodies and unusual pleiomorphic bodies. The latter type probably showed some lipofuscinic component. The relationship between type C and classical Niemann-Pick disease is discussed.