An immunohistological study of the spinal cord in 20 cases of sporadic and 4 iatrogenic (growth hormone) cases of Creutzfeldt-Jakob (CJD) disease patients was performed to detect the presence of disease specific prion protein using a number of different antisera. Prion protein was present in all the growth hormone recipients and in 11 of the 20 sporadic CJD cases. Plaque-like deposits of prion protein were found in all the growth hormone cases and three of the sporadic cases. This is the first demonstration of the topographic immunolocalisation of prion protein in the spinal cord of CJD patients, a feature which could help elucidate some important aspects of the pathogenesis of CJD.