Improvement in health care quality and safety can be notable when measurement criteria are clear, evidence is strong, and policy and interventions are focused. Despite this potential, progress in reducing patient harm in hospitals has been slow.1 In an effort to catalyze progress, the Department of Health and Human Services (HHS) is funding a national program, Partnership for Patients (P4P), with the ambitious goal of reducing “preventable hospital-acquired conditions” by 40% by 2013, focused initially on 9 complications.2 Although the program's goal formally includes only preventable harm, the HHS notes “the Partnership will target all forms of harm” and provide guidance to hospitals for reducing “all-cause harm.” Simultaneously, the list of “serious reportable events” for which the Centers for Medicare & Medicaid Services will modify physician and health care institution payment is increasing. However, delay in defining a measurement strategy for harm has slowed progress and has created confusion. The need to reach consensus on robust, pragmatic measures for assessing and tracking harm rates has therefore become urgent.