Laser-ablated iridium atoms react with O-2 to give the linear dioxide OIrO and the side-bound dioxygen adduct (O-2)IrO2 as primary reaction products, with nu(3) absorptions at 930.0 and 875.0 cm(-1), respectively. The (nu(1) + nu(3)) combination bands for these species were observed, confirming the assignments of the nu(1) and nu(3) modes for (O-2)IrO2 and providing an estimate for the nu(1) mode in OIrO. The symmetric and antisymmetric stretching modes of the Ir(O-2) ring in (O-2)IrO2 were also observed. Density functional calculations support these assignments and show that the (O-2)IrO2 species is best formulated as a peroxide with iridium in the +6 oxidation state, providing the first example of an iridium(VI) oxo complex.