The childhood ceroid‐lipofuscinoses are a group of autosomal recessively inherited disorders characterized by massive accumulation of autofluorescent lysosomal storage bodies in neurons as well as other cell types. The storage body accumulation is accompanied by severe degeneration of the central nervous system that results in blindness, cognitive and psychomotor degeneration, and premature death. On the basis of pathologic and biochemical criteria, a hereditary disease in the mnd mouse strain has been proposed as a model for certain types of human ceroid‐lipofuscinosis. Experimental evidence suggests that the storage body accumulation in humans with juvenile and late‐infantile ceroid‐lipofuscinosis is linked to altered carnitine biosynthesis. On the basis of the latter observation, a study was performed to determine whether dietary carnitine supplements could slow the disease progression in the mnd mouse model. Carnitine supplementation begun at 4 weeks of age did not slow the retinal degeneration that is characteristic of this disease. It did, however, significantly elevate brain carnitine levels, slow the accumulation of autofluorescent storage bodies in brain neurons, and prolong the lifespans of the treated animals. These findings suggest that there is a link between carnitine biosynthesis and the disease pathology and indicate that carnitine supplementation may be beneficial in slowing the disease progression in humans with certain types of hereditary ceroid‐lipofuscinosis. J. Neurosci. Res. 50:123–132, 1997. © 1997 Wiley‐Liss, Inc.