Implanted medical devices (IMDs) are extremely common, yet they are not systematically documented on hospital admission. Through structured patient interviews, we determined the prevalence of IMDs in hospital inpatients. Using medical record review, we evaluated the sensitivity of the medical record reporting of IMDs on an academic medical inpatient service. Fifty-eight percent of 191 interviewees reported 1 or more IMDs. Participants who reported greater than 1 IMD were older and had more frequent hospitalizations. The most common devices reported were surgical mesh, screws, plates, or wires (n = 47); intravascular stents (n = 25); and prosthetic joint replacements (n = 17). Forty-six patients (24%) reported greater than 1 IMD that had not been recorded in their admission history and physical examination. The prevalence of IMDs in hospitalized patients is high and underestimated in the medical record and may have significant implications for patient care.