The dynamics of formation of oxygen atoms after UV photoexcitation of SO₂ in the gas-phase was studied by pulsed laser photolysis-laser-induced fluores-cence ‘pump-and-probe’ technique in a flow reactor. SO₂ at room-temperature was excited at the KrCl excimer laser wavelength (222⋅4nm) and O(³P_j) photofragments were detected under collision-free conditions by vacuum ultraviolet laser-induced fluorescence. The use of narrow-band probe laser radiation, generated via resonant third-order sum-difference frequ ency conversion of dye laser radiation in Krypton,allowed the measurement of the nascent O(³P_j=2,1,0) ine-structure state distribution:nj=2/nj=1/nj=0=(0⋅88±0⋅02)/(0⋅10±0⋅01)/(0⋅02±0⋅01). Employing NO₂ photolysis as a reference, a value of Φ_O(³P)⁼⁰⋅13±0⋅05 for the absolute O(³P) atom quantum yield was determined. The measured O(³P) quantum yield is compared with the results of earlier fluorescence quantum yield measurements. A suitable mechanism is suggested in which the dissociation proceeds via internal conversion from high rotational states of the initially excited SO₂(C^~1B₂) (1,2,2) vibronic level to nearby continuum states of the electronic ground state.