An atomic oxygen beam and mass spectrometer were used to measure the oxygen atom reflection &ggr;16, recombination &ggr;32, general surface reaction &ggr;M, and occlusion &ggr;0 probabilities on six different engineering surface as a function of oxygen exposure. The materials studied include gold, Nichrome V, aluminum, titantium, silver, and platinum. The reflection probability was seen to range from a initial total loss (at time of exposure equal to zero) on aluminum, titantium, and plantinum to an observed maximum 0.65 on titanium after 8.5 h of exposure. Recombination was seen on all surfaces except aluminum and platinum, the maximum recombination probability &ggr;32 being 0.27 on gold after 19 h of exposure. The molecules H2O, CO, and CO2 were produced in a first-order reaction of atomic oxygen with surface hydrogen and carbon with varying probabilities.