Oncological family history allows to estimate an empirical risk to develop malignant tumors. Nowadays family history is crucial to determine the indication to perform screening of cancer predisposing genes. Five to 10% of all cancers are the result of highly penetrant genes. Most of the genes responsible for familial cancer syndromes have been characterized. It is now feasible, by a simple blood sample, to detect germ-line alterations of these genes and to identify the at risk individuals. Specific screening and preventive strategies are recommended in the management of these high risk individuals.