Following the cloning of BRCA1 and BRCA2 it has been suggested that genetic screening may be of benefit for women at high familial risk. To be able to assess whether this is the case more research is needed on the penetrance of the different mutations, their prevalence in the population, the biological and environmental factors affecting the development of cancer in mutation carriers and the natural history of genetically determined breast cancer. Furthermore, studies on the efficacy of preventive measures, on counselling and on psychological effects of testing are also needed.