A planar multi-gated cardiac blood pool acquisition is a non-invasive technique commonly used to measure left ventricular ejection fraction (LVEF). It is essential that the calculation of LVEF be accurate, repeatable and reproducible for serial monitoring of patients. Different processing modes may be used in calculating the LVEF which require various degrees of manipulation. In addition, different operators with varying levels of experience may process the same data set. It is not known whether the inter-operator variability of LVEF values within a single nuclear medicine department has the potential to affect the calculated LVEF and in turn affect patient management. The aim of the study was to determine variability of LVEF values among operators with different levels of experience using two processing modes.