In cardiac patients who received multidose cold blood potassium cardioplegia for intracardiac procedures, the intraoperative and the immediate postoperative blood potassium levels were decreased at aortic cross-clamp time below 2 hours and increased at aortic cross-clamp time above 2 hours, but they were within normal limit [not hypokalemia or hyperkalemia]. In spite of increased infusion numbers and amount of cold blood potassium cardioplegia, the postoperative blood potassium levels were similar to the postoperative levels, the immediate postoperative A-V blocks were transient and the postoperative arrhythmia were rare.