The advent of targeted anticancer therapies over the past few decades has reinvigorated the field of cancer therapeutics, with the promise of increased cancer cure rates accompanied by decreased toxicity. But, has that promise been fulfilled? The short answer is definitely 'no', both because of disappointing tumor responses and unexpectedly high toxicity, as well as the extremely high financial cost of these agents. However, failing to completely fulfill initial promise does not mean that targeted therapies should be abandoned. Increased progression-free survival might ultimately lead to increased overall survival, and targeted therapies have changed the course of cancers such as breast, lung and renal. Therefore, we would argue that despite some disappointments, targeted therapies have a vital role in future cancer treatment. This Review will discuss the positives and negatives of targeted agents, and propose a way to optimize their use and development to ensure proper personalized cancer medicine that tailors not only the anticancer treatment, but also the antitoxicity strategies, to achieve the best outcome for the patient in terms of both quality and quantity of life.