We find that breast and ovarian cancers are consistently enriched for deletions of chromosome arms 17q and 13q-harboring the <i>BRCA1</i> and <i>BRCA2</i> genes, respectively-relative to other solid tumor types, and that mutational timing analysis independently places these deletions among the earliest somatic events in these cancers. This evidence concerns the gene BRCA2 and ovarian carcinoma.