Patient misidentification errors have the potential for serious patient harm. This study analyzed the processes of care involved in 1,189 wrong-patient events. Most errors occurred during ordering/prescribing (42%). One-quarter of all events reached the patient, most commonly involving inappropriate medication administration or receiving the wrong test or procedure. Errors caught before reaching the patient were primarily attributed to information review by nurses, technicians, or other healthcare staff. The authors recommend several strategies for reducing wrong-patient errors.