The photodissociation of IO and OIO was investigated using 2-color, pulsed laser photolytic generation and dissociation of these species, combined with the detection of product atoms by resonance fluorescence. IO radicals were generated in the reactions of O(P-3) with I-2, O(P-3) With CF3I, and I(P-2(J)) with O-3 and were detected by absorption spectroscopy. The self-reaction of 10 was used as the source of OIO, which was also detected by absorption spectroscopy. The quantum yield of O(P-3) formation following the photolysis of 10 at 355 nm was measured relative to NO2 photolysis at the same wavelength and was found to be 0.91 +/- (0.19)(0.26). O(P-3) was not detected in the photolysis of OIO at 532 nm, enabling us to place an upper limit to the quantum yield of 7 x 10(-3) at this wavelength. I(P-2(J)) was detected in the 532-nm photolysis of OIO but was formed only at very high laser fluence, presumably in a sequential two-photon process, These results show that OIO is probably stable with respect to photolysis in its strong visible absorption band between approximate to 480 and 660 nm, which has: important implications for the iodine chemistry of the marine boundary layer.