During a 7.5-year period ending in June 1977, 220 patients underwent combined aortic valve replacement and myocardial revascularization. Early (30-day) mortality was 5.4% (12 patients), and was significantly affected by the development of perioperative myocardial infarction. For 23 patients with electrocardiographic and enzymatic evidence for definite infarction, hospital mortality was 17%; for 66 patients with probable infarction mortality was 5%; and for 116 patients without evidence for infarction mortality was 3%. The difference in mortality between the definite and no infarction groups was significant (p less than 0.01). The incidence of perioperative infarction was influenced by the type of myocardial protection employed during the operative procedure. Definite infarction occurred in 24% of 41 patients who had mild (28-32 degrees C), intermittent hypothermic coronary perfusion, in 9% of 142 patients with hypothermic ischemic arrest (myocardial temperature 20 to 27 degrees C) and in none of 22 patients with hypothermic, potassium-induced cardioplegia (myocardial temperature 8--18 degrees C). The difference in the rate of infarction between the coronary perfusion and the two hypothermic ischemic arrest groups was significant (p less than 0.01). The mean duration of followup for 100% of the hospital survivors was 22.5 months. Cumulative survival was 88% at 1 year and 77% at 3 years. These figures do not differ significantly from those for patients without coronary artery disease having isolated aortic valve replacement in our institution, and are superior to those reported for patients with coronary and aortic valve disease undergoing only aortic valve replacement. We conclude that combined aortic valve replacement and myocardial revascularization should be performed in all patients in whom the lesions coexist. Hypothermic ischemic arrest, preferably in combination with potassium-induced cardioplegia, provides the most myocardial protection during operation.