The RCS rat is a widely studied model of human retinal dystrophies including retinitis pigmentosa. Chondroitin-6-sulphate (C6S) in the interphotoreceptor matrix was localised immunocytochemically in both the normal congenic and dystrophic strains of the RCS rat up to 65 days postnatally. From postnatal days 5 to 15 the distribution of C6S in both strains was similar, being localised in the interstices of developing inner and outer segments and adjacent to the RPE surface. In the normal rats, the distribution of C6S did not change with age. In the RCS rats, however, at postnatal days 20 to 35 staining was observed as a dense band at the junction of inner and outer segments and no staining was observed adjacent to the surface of the RPE. At postnatal day 45 onwards there was a decrease and a complete absence of C6S staining in these rats. This change in the pattern of staining correlated with the morphological observation of the progressive degeneration of photoreceptor cells suggesting that C6S may be important in photoreceptor degeneration in the RCS rat.