Hospitalized patients continue to suffer iatrogenic harm, according to this study of Medicare patients completed by the Office of the Inspector General (OIG). Using methodology similar to the landmark Harvard Medical Practice Study, this study found that 13.5% of hospitalized Medicare patients experienced an adverse event, of which nearly half were considered preventable. However, fewer than 2% of patients experienced either a never event or a preventable complication for which hospitals are no longer reimbursed by the Centers for Medicare and Medicaid Services. These results are similar to the OIG's prior 2008 report. Based on these results, OIG recommends further efforts to accurately measure adverse events, and also recommends broadening the "no pay for errors" policy. The challenges of accurately measuring safety problems are discussed in an AHRQ WebM&M commentary.