Decomposition of hydrogen peroxide with a hypervalent iodine compound was examined. The results indicate that treatment of a hypervalent iodine compound with hydrogen peroxide produces singlet molecular oxygen ((1)O(2)). Convergent evidence for the production of singlet molecular oxygen ((1)O(2)) by decomposition of hydrogen peroxide with a hypervalent iodine compound comes from chemical trapping experiments and the specific chemiluminescence detection of (1)O(2) at 1270 nm. Substantial evidence demonstrates that hydroperoxyl radical produced from hydrogen peroxide with hypervalent iodine reacts via a tetraoxidane intermediate, decomposing to give singlet molecular oxygen.