Abstract
Nineteen North American Caucasian families that contain a minimum of four confirmed cases of breast or ovarian cancer have been studied. Four polymorphisms (cLB17.1, D17S579, D17S588, and D17S74), which span a region of approximately 15 cM on chromosome 17q12, were typed. Our data confirm the location of a dominant gene conferring susceptibility to breast and ovarian cancer (maximum lod = 9.78) and suggest that the breast-ovarian cancer syndrome is genetically heterogeneous. Two recombinants in one large family suggest that the breast-ovarian cancer locus lies between D17S588 and D17S579.