In Phase II, a myocardial infarction registry was established to include all patients hospitalized in the area with a discharge diagnosis of acute myocardial infarction. The registry placed the trial findings in a community-based perspective and aided in the interpretation of trial findings by assessing the proportion of cases seeking paramedic care and determining the characteristics of these patients in contrast to those arriving at the hospital by other means. The records of all patients admitted directly to coronary care units in Seattle and King County were surveyed. Study personnel examined differences, if any, between paramedic and other transport groups regarding clinical history, treatment, complications, and hospital discharge rates. Of the cases in the registry, 300 who arrived at the hospital by means other than paramedic transport were compared to the paramedic-transported cases with respect to the incidence of new Q-wave infarction on the first and last electrocardiogram, an interview to determine onset, severity, and duration of symptoms, and reasons for choosing one type of care over the other during the emergency situation.