Cheviot sheep from the Neuropathogenesis Unit flock were examined for PrP in brain sections using immunocytochemistry in order to aid scrapie diagnosis. Brains were collected from sheep which had been naturally or experimentally infected with scrapie and fixed in periodate-lysine-paraformaldehyde or in formalin. Immunolabelling was achieved using a monoclonal antibody (FH11) raised to the N-terminus of recombinant PrP protein. Several pre-treatments were studied in an effort to enhance PrP immunolabelling such as trypsin, formic acid and hydrated autoclaving. Trypsin was successful in highlighting PrP staining in formalin-fixed tissue. PrP staining was regularly observed in the dorsal vagus nucleus of the medulla oblongata and in the thalamus. Differences in the distribution and intensity of PrP immunostaining were apparent between the scrapie sources ME7 and SSBP/1.