The finding that poly(ADP-ribose) polymerase inhibitors, a new class of DNA repair inhibitors, specifically kill cancer cells with BRCA1 or BRCA2 mutations but are less cytotoxic to normal cells highlighted the promise of DNA repair inhibitors for targeted cancer treatment.1, 2 This finding also provides proof of the principle that synthetic lethality interactions in the DNA repair network can be exploited for targeted cancer therapy. This evidence concerns the gene BRCA2 and cancer.