The proportion of all breast or breast/ovarian cancer families in our population attributable to recurring BRCA1 or BRCA2 mutations appears to be lower than in some other countries such as Iceland (Thorlacius et al, 1997), Israel (Levy-Lahad et al, 1997) or Norway (Moller et al, 2001), comparable to that in the Netherlands (Peelen et al, 1997; Claes et al, 1999), but much higher than in others, such as Italy (Szabo and King, 1997; Cippolini et al, 1999), and sufficient to have practical implications for the formal organisation of molecular screening. The gene discussed is BRCA1; the disease is ovarian cancer.