The photochemistry of chlorine dioxide (OClO) is investigated by two-color time-resolved resonance Raman spectroscopy. Pump and probe wavelengths of 390 and 260 nm, respectively, are used to monitor photoproduct formation following aqueous OClO photoexcitation. Depletion and subsequent recovery of the OClO scattering intensities is observed consistent with subpicosecond reformation of OClO via geminate recombination of the primary photoproducts. Intensity is observed at 1442 cm(-1) consistent with ClOO formation that appears and decays with time constants of 27.9 +/- 4.5 ps and 398 +/- 50 ps, respectively. The results presented here represent the first direct evidence for ClOO formation following the photoexcitation of aqueous OClO.