Many hereditary cancer syndromes have been described where a germline mutation in a tumour suppressor gene causes hereditary predisposition to cancer in a family. Most of the causal genes are known and DNA-based molecular genetic presymptomatic testing of individuals at risk is possible. The Li-Fraumeni syndrome caused by germline mutations in the p53 gene differs from the majority of cancer syndromes by the wide spectrum of cancers which can occur in the mutation carriers. This makes the medical, psychological and ethical problems of presymptomatic genetic testing for familial cancer even more pronounced in this syndrome. Any DNA analysis in hereditary cancer cases has to be therefore preceded by extensive genetic and psychological counselling.

        Key words: familial cancer, tumour suppressor genes, Li-Fraumeni syndrome, germline p53 mutations, pre- symptomatic genetic testing.