Nerve conduction, EEG, visual evoked potentials, electroretinograms and somatosensory evoked potentials were investigated in 3 children with the Bielschowsky-Jansky-type and in 1 child diagnosed as Spielmeyer-Vogt-type of neuronal ceroid lipofuscinosis. Electroretinographic responses were abolished in all of them. Electroencephalograms showed high amplitude, irregular delta-theta activity and spike- or polyspike-wave discharges without localized preponderance. As a characteristic feature for the Bielschowsky-Jansky type grossly enlarged evoked responses to single light flashes were recorded. Somatosensory evoked potentials were increased in amplitude in 2 patients. Myoclonic jerks of the pyramidal type could be elicited by electrical stimuli to the median nerve. The possibility to differentiate certain neurometabolic disorders of childhood by simple electrophysiological parameters is discussed.