Steve Elledge and colleagues have developed a bioinformatic method called TUSON Explorer to identify candidate tumor suppressor genes (TSGs) and oncogenes (OGs) based on sequence mutation parameters (Cell doi:10.1016/j.cell.2013.10.011, 31 October 2013). They applied the method to tumor sequence data from the COSMIC and TCGA databases and identified an estimated 320 TSGs and 250 OGs, including many new potential cancer drivers. Interestingly, their analyses predict that many TSGs are haploinsufficient, and they identified an enrichment of candidate TSGs on the X chromosome and 2 potential TSGs on the Y chromosome. The authors determined the density of TSGs and OGs on each chromosome arm and found that arms with a high density of TSGs have a high frequency of deletion and low frequency of amplification, whereas arms with a high density of OGs have a low frequency of deletion and a high frequency of amplification. A similar analysis of whole-chromosome aneuploidy also showed that density of tumor drivers associates with frequency of chromosome losses and gains. The authors conclude that there are likely to be many more cancer driver genes than previously thought and that there is a long tail of tumor driver genes with weak effects.