Photon stimulated desorption (PSD) from KEKB factory copper chambers was measured at the National Synchrotron Light Source (NSLS), located at the Brookhaven Laboratory. The KEKB is an asymmetrical collider recently constructed in Ibaraki, Japan. The collider utilizes two UHV ring chambers. one for a 3.5 GeV positron beam and the other for an 8 GeV electron beam, for B-meson studies. Two each, 1 m long, 94 mm inner diameter, chemically deoxidized copper beam chambers with conflat end flanges, were provided by KEKB to the NSLS, for measurement of PSD. PSD and specular reflection were measured on NSLS VUV ring beamline U9a. It has been reported that a high temperature air bake on large stainless steel vacuum systems reduces the need for a vacuum bake. To determine the effect of surface oxide, following the initial PSD measurement, the chambers were chemically cleaned and then oxidized in air for a week at 150 degreesC. PSD was remeasured after the air bake. A similar process and measurement was performed on a stainless steel beam chamber, with the exception of oxidation at 450 degreesC. After the chambers were installed on beamline U9a, they were exposed to a minimum of 10(23) photons direct from the source having a critical energy of 595 eV, striking at an incident angle of 100 mrad. The major PSD yields for hydrogen, carbon monoxide, carbon dioxide, methane, and water vapor are reported as a function of accumulated photon flux, incident surface oxide, and chamber preparation. The results are compared with other PSD measurements on NSLS beamlines and those of other laboratory publications for copper and stainless steel.