Collisional activation, charge reversal, and six different neutralization-reionization mass spectrometric experiments with [H-2,O-2](.+) radical cations and [H-2,O-2](.-) radical anions were performed in order to probe the predicted existence of neutral water oxide, H2OO, the long sought after tautomer of hydrogen peroxide, HOOH. The experiments together with ab initio calculations indicate that H2OO is a local minimum on the [H-2,O-2] potential-energy surface, and the elusive molecule seems to be formed as a transient upon neutralization of the corresponding radical cation H2OO.+ in the gas phase.