Films selected for anticipated reaction with atomic oxygen, namely carbon, silver, and osmium, were exposed during the Shuttle STS-4 mission. A silver film 225¿5 nm thick was converted to a transparent blue-green interference film 355¿5 nm thick. Both carbon and osmium films 10-30 nm thick apparently formed volatile oxides and disappeared, except where well shielded. A calculated total of approximately 7¿1019 oxygen atoms per cm2 struck the surfaces, which could have removed on the order of 3 &mgr;m of material if only 10% reacted. The absence of apparent effects on adjacent thin and thick gold films is offered as evidence that sputtering is not responsible.