Aim and METHODS: The aim of this health technology assessment was to analyse the current scientific and genetic counselling situation about predictive genetic testing for hereditary breast and colorectal cancer. This report is based on a systematic literature research and on a specific health technology assessment (CCOHTA) resp. review (American Gastroenterological Ass.). Background: Breast and colorectal cancer are counted among the most frequently cancer diseases. 5-10% show a familial determination. A hereditary modified gen is responsible for the increased cancer risk. Results and CONCLUSION: The identification of the responsible gen defect in an affected family member is important. If the test result is positive there is an uncertainty about if the desease will occur, when and in which degree founded in the geno-/phenotype correlation. The individual risk estimation is based upon empirical evidences. The so-called preventive medical check ups are early detection examinations. For colorectal cancer the evidence about early detection methods is better than for breast cancer. Prophylactic mastectomy (PM) reduces the relativ breast cancer risk by approxemately 90%. Colectomy can be used as a prophylactic (FAP) and therapeutic method. After operations the cancer risk remains high and so early detection exeminations are still necessary. The evidence is often fragmentary and from limited qualit. New identifications of mutations and demand creation will result in an increase of predictive genetic counselling and testing. There is a gap between predicitve genetic diagnosis and the prediction, prevention, early detection and surgical interventions. Since predictive genetic diagnosis is a very sensitive issue it is important to deal carefully with it in order to avoid inappropriate hopes.