This statewide public telephone survey in Massachusetts found that more than 20% of respondents experienced a medical error in the prior 5 years, and more than half of these incidents resulted in harm. Prior patient surveys have brought to light previously unrecognized safety problems, although discrepancies have been shown to exist between patient reports and other methods for detecting adverse events. Most respondents attributed adverse events to individual physicians and nurses rather than health systems, underscoring the challenge of conveying blame-free culture and systems approaches to the public. Diagnostic errors were the most common type of error reported. About half of patients who experienced medical errors reported the incident to a clinician, hospital, or official agency. Most patients did not look for safety or quality information in choosing a physician or hospital, and only a third of respondents view patient safety as a serious problem for the state. Importantly, prior to being given an explanation, less than half of respondents understood the term "medical error." These findings emphasize the divide between the high prevalence of safety hazards and the lack of public awareness of patient safety efforts and policy.