We and others have recently reported that patients with the Gerstmann-Sträussler-Scheinker syndrome have a mutation at codon 102 of the gene coding for amyloid protein that accumulates in this disease. We report here that this mutation was not found in 5 familial and 27 sporadic cases of Creutzfeldt-Jakob disease or in 3 patients with kuru, so that although this mutation may be responsible for amyloidogenesis and transmissibility in Gerstmann-Sträussler-Scheinker syndrome, it cannot be the only cause of human spongiform encephalopathy.