Recently, balloon aortic valvuloplasty has been proposed for the treatment of severe aortic stenosis in elderly patients when aortic valve replacement has been declined or deferred. The natural history of these patients has not been clearly defined. Therefore, to develop a comparison cohort of patients with unoperated aortic stenosis, we reviewed the records of all Mayo Clinic patients in whom severe aortic stenosis had been diagnosed during the period 1978 through 1985 but no surgical procedure had been performed because the patient declined or the physician deferred this option. Among the 50 patients identified (36 men and 14 women; mean age 77 years, range 60 to 89 years), an operation was declined by 28 and deferred in 22. The diagnosis of aortic stenosis was established clinically by a cardiologist in all 50 patients and independently confirmed by echocardiography, Doppler ultrasonography, or catheterization in 47 of the 50. All patients were symptomatic. Follow-up was complete to September 1986 or death in all 50 patients. Actuarial survival at 1, 2, and 3 years was 57, 37, and 25%, respectively. Survival of age- and sex-matched control subjects was 93, 85, and 77%, respectively (P less than 0.0001 at each 1-year interval). At last follow-up, only 13 of the 50 patients (26%) were alive. A cardiac cause was cited for 36 of the 37 deaths. Because of the poor survival in this group of patients, evaluation of alternative nonsurgical therapeutic modalities such as balloon valvuloplasty is imperative when operative intervention is declined or deferred in elderly patients.