Left ventricular ejection fraction was measured by gated wall motion in 62 patients, 75 years old or older, admitted to a Geriatric Acute Assessment Ward. From this group, 42 patients not taking digitalis or other cardioactive medication were selected for analysis. Thirty of them had clinically identifiable heart disease, whereas 12 did not. Resting left ventricular ejection fractions in the 12 patients without clinically identifiable heart disease averaged 0.60 +/- 0.09. None had an ejection fraction below 0.50. In the 30 patients with clinically identifiable heart disease, mean ejection fraction was 0.49 +/- 0.15 (range 0.17-0.84), P less than 0.01. In the patients with heart disease, reduction of ejection fraction was correlated with either cardiac enlargement or congestive heart failure. Neither age nor electrocardiographic abnormalities added to the strength of this correlation. Fifty-eight per cent of patients with congestive heart failure had ejection fractions greater than or equal to 0.40, suggesting that congestive heart failure in this age group is frequently related to diastolic left ventricular dysfunction unaccompanied by major systolic dysfunction. The prognosis of patients with congestive heart failure and ejection fractions above 0.35 was significantly better than of patients with congestive heart failure and ejection fractions below 0.35. From these data and other data available in the literature, it is proposed that the lower limit for ejection fraction be 0.50 for patients 75 years old or older. Congestive heart failure in patients 75 years old or older appears to be associated with relatively higher ejection fractions or even with ejection fractions within the normal range. In these patients, digitalis may not be indicated, and short term-prognosis is relatively favorable.