Counselling, risk assessment and surveillance are provided for women with a significant family history of breast cancer through a network of clinical centres across the United Kingdom. Before 2004, the recommended minimum 'threshold' for significant familial risk was set by a number of guidelines issued, which broadly required one first-degree relative diagnosed with breast cancer before age 40 or two close relatives both diagnosed before age 60. In 2004, NICE issued detailed guidelines in which the age requirement for two affected relatives was removed. However, it is widely recognised that the evidence base for any specific minimum threshold is limited and that there is a need for empirical studies to validate current and future recommendations. That is the object of the present study.