In a sibship of ten, three brothers presented with an adult form of ceroid-lipofuscinosis. The diagnosis was confirmed by necropsy of the first patient and was made by electron microscopy of eccrine sweat glands and of skeletal muscles in the two others. Somatosensory evoked potentials were characterised by biphasic, nearly monophasic, very high voltage complexes totally unlike those found in normal controls. Similar sensory evoked potentials were however recorded in other types of ceroid-lipofuscinosis. While electron microscopy of easily available tissues gives fairly specific results, sensory evoked potentials can bring supportive diagnostic evidence in adult ceroid-lipofuscinosis.