The announcement by President Obama of a precision medicine initiative created excitement in the medical community. The president referred not to personalized medicine but to “precision medicine,” a term given profile by a recent publication from the National Research Council,1 in which the authors explain that their use of “precision” was intended to avoid the implication that medications would be synthesized personally for single patients. Rather, they hoped to convey a broader concept that would include precisely tailoring therapies to subcategories of disease, often defined by genomics.