Retained surgical instruments are among the most dramatic of medical errors, and are considered never events. Although these errors are rare, prior studies in adults have defined risk factors for retained instruments, which include emergency surgeries and intraoperative changes in the surgical plan. This study examined the problem of retained foreign bodies in pediatric surgery, using cases identified by the AHRQ Pediatric Quality Indicators. Gynecologic surgeries emerged as the only type of surgery significantly associated with an increased risk of retained instruments, and retained foreign bodies were associated with increased hospital length of stay and costs (but not increased mortality). Despite the persistence of this problem, controversy remains around how to prevent such errors.