Background. The frequency and determinants of early rapid diastolic filling abnormalities in the community and in cardiac patients are poorly understood. Methods and Results. Early left ventricular (LV) rapid filling was assessed via equilibrium radionuclide angiocardiography in 70 community volunteers (LV ejection fraction [EF] >= .50) and 778 cardiac patients, all aged at least 45 years. The frequency of early rapid filling and the independent clinical, therapeutic, and hemodynamic variables predictive of early rapid filling abnormality were determined. Depending on the parameter assessed, early rapid filling was abnormal in 27% to 54% of the community volunteers, 34% to 53% of cardiac patients with an LVEF of 0.50 or greater, and 42% to 67% of cardiac patients with an LVEF lower than 0.50. On the basis of multivariate analysis, models of clinical, therapeutic, and hemodynamic variables were modestly predictive of early rapid filling abnormality. Age, sex, valvular insufficiency, hypertension, digoxin use, and heart rate were independent determinants of early rapid filling. Conclusions. In participants aged older than 44 years, early rapid filling was frequently abnormal in the community volunteers and in patients with an LVEF of 0.50 or greater and was most common in patients with an LVEF lower than 0.50. Clinical, therapeutic, and hemodynamic variables had modest independent predictive value for early rapid filling abnormality.