Increased expression of clusterin mRNA is associated with neurodegenerative states, including retinas affected by retinitis pigmentosa (RP). We have investigated the distribution of immunoreactive clusterin in normal and RP-affected retinas. Reactivity at the inner limiting membrane, plexiform layers, and photoreceptors in normal retina accords well with clusterin's postulated role as a membrane protective agent. In RP-affected retina the organized distribution is lost and overall reactivity appears decreased. The changes in this case may reflect increased turnover or removal of clusterin, perhaps via interaction with components of the immune system.