Structure-based approaches now impact across the whole continuum of drug discovery, from new target selection through the identification of hits to the optimization of lead compounds. Optimal application of structure-based design involves close integration with other discovery technologies, including fragment-based and virtual screening. Here, we illustrate the use of structural information and of structure-based drug design approaches in the discovery of small-molecule inhibitors for cancer drug targets and provide an outlook on the exploitation of structural information in future cancer drug discovery. Examples include high profile protein kinase targets and structurally related PI3 kinases, histone deacetylases, poly(ADP-ribose)polymerase and the molecular chaperone HSP90. Structure-based design approaches have also been successfully applied to the protein-protein interaction targets p53-MDM2 and the Bcl-2 family.