To determine the relative prognostic significance of location (anterior or inferior) and type (Q wave or non-Q wave) of infarction, the hospital course and follow-up outcome (mean duration 30.8 months) of 471 patients with a first infarction were analyzed. Analyses were performed grouping the patients according to infarct location (anterior, n = 253; inferior, n = 218), infarct type (Q wave, n = 323; non-Q wave, n = 148), and both location and type (inferior non-Q wave, n = 85; inferior Q wave, n = 133; anterior non-Q wave, n = 63; and anterior Q wave, n = 190). Patients with anterior infarction had a substantially worse in-hospital and follow-up clinical course compared with those with inferior infarction, evidenced by a larger infarct size (21.2 versus 14.9 g Eq/m2 creatine kinase, MB fraction [MB CK], p less than 0.001), lower admission left ventricular ejection fraction (38.1 versus 55.3%, p less than 0.001) and higher incidence of heart failure (40.7 versus 14.7%, p less than 0.001), serious ventricular ectopic activity (70.2 versus 58.9%, p less than 0.05), in-hospital death (11.9 versus 2.8%, p less than 0.001) and total cumulative cardiac mortality (27 versus 11%, p less than 0.001). Patients with Q wave infarction similarly experienced a worse in-hospital course compared with patients with non-Q wave infarction, evidenced by a larger infarct size (20.7 versus 12.7 MB CK g Eq/m2, p less than 0.001), lower admission left ventricular ejection fraction (43.7 versus 50.6%, p less than 0.001), and a higher incidence of heart failure (31.9 versus 21.6%, p less than 0.05) and in-hospital death (9.3 versus 4.1% p less than 0.05). However, there was no increased rate of reinfarction or mortality in hospital survivors with non-Q wave infarction compared with those with Q wave infarction, and total cardiac mortality was similar (16 versus 21%, p = NS). To evaluate the role of infarct location and type independent of infarct size, patients were grouped according to quartile of infarct size, and outcome was reanalyzed within each group. Patients with anterior infarction demonstrated a lower left ventricular ejection fraction on admission and after 10 days than did patients with inferior infarction, even after adjustment for infarct size, as well as a higher incidence of congestive heart failure and cumulative cardiac mortality.(ABSTRACT TRUNCATED AT 400 WORDS)