We screened 111 cases of sporadic Creutzfeldt-Jakob disease (CJD) and 75 healthy control subjects in Japan to detect possible polymorphisms in their prion protein gene (PRNP). We identified a G-to-A point substitution at codon 210, leading a valine-to-isoleucine change, in a 69-year-old CJD patient. This substitution was not seen in 75 healthy control subjects.