Results of PrP gene analysis in 5 of 9 members from a Jewish Tunisian family with Creutzfeldt-Jakob disease (CJD) showed a mutation at codon 200 involving substitution of lysine (Lys200) for glutamic acid (Glu200). This observation suggests that Lys200 allele probably tracks with CJD in this family and supports the possible genetic basis of the disease in the Mediterranean cluster. A second PrP variant not associated with Lys200 allele involving a short deletion in the coding sequence has also been found in only one subject.