The neuronal ceroid lipofuscinoses (NCL) are a relatively frequent group of progressive neurodegenerative disorders in children with similar, but not identical, clinical and morphological features, entailing different clinical groups, some of which have been found to represent different genetic entities, ie, infantile (INCL) or CLN1, late-infantile (LINCL) or CLN2, juvenile (JNCL) or CLN3, and a Finnish variant of LINCL or CLN5. Within the clinical pentad are included seizures, motor disturbances, visual impairment, dementia, and familial occurrence in an autosomal-recessive fashion. The ultrastructure of accruing lipopigments is diagnostically required to recognize an individual patient's NCL by showing granular lipopigments in INCL, curvilinear profiles (with or without fingerprint profiles) in LINCL and fingerprint profiles (with or without curvilinear profiles) in JNCL. Identification of genes for INCL and JNCL, together with electron microscopy in LINCL, allows safe prenatal diagnosis which is still impossible by biochemical techniques, unlike other lysosomal disorders. However, both cause and pathogenesis of the individual forms of NCL are still unknown, and therapy is gravely insufficient.