The aim of this study is to find out if the PALB2 gene is likely to play a significant role in breast cancer susceptibility in Iceland, by linkage analysis of high-risk non-BRCA1/2 breast cancer families with markers closely surrounding the PALB2 gene to test the possibility of a highly penetrant mutation, and by screening for the Finnish 1592delT founder mutation in the family members and a large group of unselected breast cancer patients. This evidence concerns the gene PALB2 and breast cancer.