The neuronal ceroid lipofuscinoses are a heterogeneous group of inherited degenerative disorders of the central nervous system. Cases of ceroid lipofuscinosis with cytoplasmic storage of granular osmiophilic deposits are associated with reduced activity of palmitoyl-protein thioesterase-1 (PPT-1) and mutations in CLN1, and occur from infancy to adulthood. We present clinical and diagnostic investigations in six children with variant late infantile neuronal ceroid lipofuscinosis and mutations in CLN1. The main clinical features at onset were behavioral disturbances and cognitive decline. Myoclonic jerks constituted the most prominent paroxysmal phenomenon. An electroencephalogram revealed the "vanishing" pattern described in infantile ceroid lipofuscinosis. Neurologic regression was associated with dramatic shrinkage of cortical structures, evident upon brain magnetic resonance imaging. Three unrelated children harboring the same homozygous mutation in CLN1 and a girl who carried a novel mutation resulting in skipping of multiple exons presented with a similar clinical phenotype. The most severe picture occurred in two siblings who carried a homozygous mutation predicting a prematurely truncated protein. Similar to the infantile form, the clinical evolution in this group of patients was characterized by an onset of severe neurologic impairment, peaking within a relatively short period of time, followed by a slower evolution of the disease.