Therapies that target cancers according to their characteristics (estrogen receptor +ve or –ve, for example) have been a major development in treating cancers successfully and have led to an increase in survival rates. These successes have led to increased research into even more tightly focused therapies. But targeted therapies do not work for everyone, raising issues of (1) identifying patients and (2) developing therapies that reflect our increasing understanding of the complex and differentiated traits of tumors. New targeted therapies such as small molecule signal transduction inhibitors and monoclonal antibodies are being developed to address tumors at all stages of the cell proliferation cycle and it is hoped that they may eventually transform cancer into a fully treatable condition.