Photodepletion efficiencies of O-2(a) on stepped Pt(335) and Pt(779) surfaces have been measured for ultraviolet light in the range 3.87-4.77 eV, using temperature programmed desorption to separate photodepletion processes from step and terrace sites. The O-2 photodepletion at the (001) step sites is faster by a factor of 2 or 3 than at the (111) terrace sites. The larger cross section for O-2 photodepletion at Pt step sites compared to smooth (111) Pt terrace sites may be due to chemical differences between O-2 on the two types of sites or to the presence of an enhanced lifetime for photoexcited electron states at step sites.