We report on clinical, electrophysiological, neuroradiological, and morphological data from 19 patients with different types (late infantile, juvenile, and adult) of neuronal ceroid-lipofuscinosis (NCL), observed in the last 10 years at the Neurological Institute of Milan. Late Infantile NCL (LINCL) (8 patients, 4m/4f). Age at onset: 2-4 1/2 years. Seizures (6 patients) or decline of mental capacities (2 patients) were the presenting symptoms, followed by myoclonus and ataxia; visual loss and optic atrophy occurred in 6 patients within 3 years. All but 2 children became bedridden within 3 1/2 years. CT and MRI demonstrated different degrees of cerebral and cerebellar atrophy within 3 years from onset of the disease. Ultrastructural studies showed fingerprint profiles (FP) and osmiophilic bodies (OB) in circulating lymphocytes; curvilinear bodies (CB) and FP were detected in eccrine secretory cells. Juvenile NCL (JNCL) (7 patients, 4m/3f). Age at onset: 6-9 years. Visual loss with retinal degeneration was the presenting symptoms, accompanied in all but 2 patients by slight mental impairment. Seizures occurred within 2-4 years. CT and MRI detected cerebral or cerebellar atrophy in those patients (5 patients) with a clinical follow-up longer than 4 years. Electron microscopy showed FP on circulating lymphocytes, and both FP and CB on skin biopsy specimens. Adult NCL (ANCL) (4 patients, 3 m/1f). Age at onset: 12-50 years. Progressive myoclonus epilepsy (1 patient) or dementia with motor disturbances (3 patients) were the clinical phenotypes of the disease. MRI demonstrated cerebral and cerebellar atrophy within 6 years from onset. Electron microscopy disclosed FP in cytoplasmic vacuoles inside eccrine secretory cells.