This article represents the first comprehensive assessment of hormetic effects of chemotherapeutic agents. Hormetic dose-response relationships were reported for a wide range of chemotherapeutics, including antibiotics, antiviral, and antitumor agents as well as substances that affect hair growth, prostate function, cognitive performance, and numerous other endpoints. Particular attention was given to assessing the quantitative features of the dose response, the underlying mechanistic features of the biphasic nature of the dose response, and the clinical implications of hormetic responses. Recognition of the hormetic-like biphasic nature of the dose response is expected to have an important impact on the design of experiments to assess chemotherapeutics and how such agents may be employed more successfully in clinical applications.