Twenty children, aged 10.3 +/- 4.5 (3.3 to 17.5) years, were studied by equilibrium radionuclide angiography to establish a normal range for diastolic parameters. Ejection fraction (EF), peak ejection rate (PER) and time to peak ejection rate (TPER), peak filling rate (PFR) and time to peak filling rate (TPFR) were obtained from ventricular time-activity curves and their first derivative curves, and PFR and TPFR were considered as the diastolic parameters. Normal ranges obtained were as follows: EF, 60 +/- 8%; PER, 3.73 +/- 0.70 EDV-1; TPER, 109 +/- 25 ms; PFR, 3.84 +/- 0.51 EDVs-1; TPFR, 136 +/- 21 ms. There were significant correlations between PER and EF (P less than 0.001), PFR and EF (P less than 0.05), while age and heart rate had no influence upon these variables. Such normal ranges will be useful for evaluation of systolic and diastolic function in children with heart disease.