Cancer therapy directed at specific, frequently occurring molecular alterations in signaling pathways of cancer cells has been validated through the clinical development and regulatory approval of agents such as Herceptin for the treatment of advanced breast cancer and Gleevec for chronic myelogenous leukemia and gastrointestinal stromal tumors. While most novel, target-directed cancer drugs have pregenomic origins, one can anticipate a postgenomic wave of sophisticated "smart drugs" to fundamentally change the treatment of all cancers. With these prospects, interest in this new class of therapeutics extends from basic research scientists to practicing oncologists and their patients. An extension of the initial successes in molecular oncology will occur more quickly and successfully through an appreciation of lessons learned with the first group of agents in their progress through clinical development.