Recent studies indicated that gaseous halogens mediate key tropospheric chemical processes. The inclusion of halogen-ozone chemistry in atmospheric box models actually closes the similar to 50% gap between estimated and measured ozone losses in the marine boundary layer. The additional source of gaseous halogens is deemed to involve previously unaccounted for reactions of O-3(g) with sea surface water and marine aerosols. Here, we report that molecular iodine, I-2(g), and iodine monoxide radical, IO(g), are released ([I-2(g)] > 100[IO(g)]) during the heterogeneous reaction of gaseous ozone, O-3(g), with aqueous potassium iodide, KI(aq). It was found that (1) the amounts of I-2(g) and IO(g) produced are directly proportional to [KI(aq)] up to 5 mM and (2) IO(g) yields are independent of bulk pH between 2 and 11, whereas I-2(g) production is markedly enhanced at pH < 4. We propose that O-3(g) reacts with I- at the air/water interface to produce I-2(g) and IO(g) via HIO and IOOO- intermediates, respectively.