Germline mutations within a defined region of the p53 gene have recently been found in families with the Li-Fraumeni syndrome (LFS). In the present study this region of p53 was sequenced in affected individuals from 8 families with LFS. In only 2 of them were such mutations detected. Our findings suggest that the p53 mutation could be the primary lesion in some but not all families with LFS, and confirm that there is a "hot spot" for these mutations at the CpG dinucleotide moiety of codon 248. Assigning risks and counselling families on the basis of presence of p53 mutations should be approached with caution.