Equilibrium pool scintigraphy was performed in 11 obese subjects (BMI 34 +/- 2) and in 14 normal control subjects. Temporal and spatial smoothing of the data was then performed followed by time-activity curve generation using a semiautomatic second derivative edge-detection algorithm. The increase in counts during the first third of diastole divided by the total change in number of counts during diastole was determined as the one-third filling fraction. This index of diastolic filling was significantly decreased in obese subjects as compared to the control group. These findings indicate that diastolic abnormalities may be an early finding in obesity-linked heart disease, occurring in the presence of normal systolic function (E.F. = 65 +/- 5%).