The neuronal ceroid-lipofuscinoses (NCLs) are a group of recessively inherited diseases characterized by progressive neuronal loss, accumulation of intracellular lipofuscin-like autofluorescent storage material with distinctive ultrastructural appearance, and clinical signs and symptoms of progressive neurodegeneration. Initially classified by the age of onset of clinical signs and symptoms as well as the ultrastructural morphology of the storage material, the growing family of NCLs can now also be biologically classified by their underlying genetic defects. For a few NCLs, we now understand the functions of the proteins encoded by the NCL genes, which has enabled refining of the diagnostic algorithms and ignited hopes for finding effective treatments in the future. Ongoing research into understanding the functions of the remainder of the NCL proteins as well as continuing advancements in technology (such as massively-parallel gene sequencing) has and will continue to inform the clinical approach, diagnostic algorithms, and treatment strategies.