The researchers created a file for each patient that included information from the patient's medical record and from a telephone interview. The telephone interview occurred 2 to 5 weeks after the patient left the hospital. The interviewers asked about patients' health, symptoms, and medical care since hospital discharge. Two of the researchers reviewed each file to determine whether an adverse event occurred. Adverse events included new or worsening symptoms, unanticipated health care visits, or deaths. For each adverse event, they rated its severity and gave their opinion about whether the event could have been prevented or made less severe.