The major protein component of the storage bodies in the late infantile (LIB) and juvenile (JB) forms of Batten diseases is subunit c of ATP synthase (subunit c). Ultrastructurally the stored material may appear as curvilinear bodies, fingerprint profiles, or a mixture of both, dependent upon the form of Batten disease and the cell type. The mnd/mnd mouse, an animal model for Batten disease, also stores subunit c and has loosely stacked lamellae within the neurons of the brain and in other cells and tissues. Using a range of tissue samples, immunolocalization, using avidin-biotin techniques at the LM level and postembedding immunogold-labelling (5 nm) with silver enhancement at the EM level, were used to investigate specific subunit c immunoreactivity. Subunit c storage was displayed in a number of cells, including neurons, muscle cells, adipocytes, macrophages, endothelial and some epithelial cells, and exocrine and endocrine cells. By EM, subunit c was localized to all curvilinear-type storage bodies, but to nowhere else within the cell. It was not present over fingerprint profiles, the characteristic storage pattern of neurons within the JB gut, possibly due to steric factors. Preliminary studies in the mnd mouse showed subunit c immunoreactivity localized to storage profiles seen ultrastructurally in neurons of the brain, and liver and heart cells. We suggest that accumulation and distribution of subunit c within a variety of cell types, and its consistent absence in others, may be related to the particular cell type's longevity and its metabolic demand.