We report on 30 cases of neuronal ceroid lipofuscinoses (NCL), mainly diagnosed in 1985-1993 in Argentina, whose population is predominantly of European descent. 'hentyfour cases were late infantile Jansky-Bielschowsky (LINCL) and 6 were juvenile Spielmeyer-Vogt (JNCL). Sex ratio was female:male, 20:lO. Age range and mean at onset and at diagnosis for the LINCL cases were 1 4 years, mean 3.1, and 2-11 years, mean 5.5, and for the JNCL cases, 5-9 years, mean 7, and 9-18 years, mean 13, respectively. Cases were referred for biopsy after neurological examination, and most included complete electrophysiological [electroencephalography (EEG) with photic stimulation, electroretinography (ERG), and visual-evoked potential (VEP)], neuroimaging, and neurometabolic investigation. NCL was the first suspected clinical diagnosis, followed by mitochondria1 encephalopathy in some cases of recent onset. Except for 1 case, clinical findings were homogeneous in LINCL, characterized by refractive epilepsy, mental regression and progressive deterioration, ataxia, myoclonia, and visual loss. Abnormal VEP, ERG, and EEG, with polyphasic high-voltage spikes when photic stimulation was performed at low frequency, were observed. Vi- sual impairment and retinitis pigmentosa were early manifestations in 416 JNCL, followed by mental abnormalities, motor deterioration, and myoclonic jerks, while 2/4 followed an atypical course. In both variants inheritance was autosomal-recessive. Five out of 27 families had more than 1 affected