A microwave-initiated plasma (2.44 GHz) flow system has been developed to generate and detect atomic oxygen as a function of distance from the discharge exit. It was found that an increase in power or a decrease in pressure resulted in larger amounts of atomic oxygen at specific points downstream from the discharge. Flow rate had little effect on the production of atoms, but increasing the flow rate did result in increasing the yield of oxygen atoms. The largest dissociation measured was 70% at a pressure of 12 Torr, a flow rate of 0.4 cm3/sec, and 500 W of absorbed power.