The problem of gas evolution in electron-positron storage rings due to synchrotron radiation was explored. The spectral distribution of the radiation was first computed. From this and from data on quantum efficiency it was possible to determine an upper limit to the resultant photoemission from the ring walls. Measurements of the desorption efficiency from stainless steel 304 then made possible a determination of the maximum gas load which could be expected as a result of the synchrotron radiation. This treatment was applied to a planned storage ring to be built at Frascati. From this it appeared that with modest processing the ring walls could be put into a condition such that the gas evolution would have completely acceptable values. The effects of wall temperature and of processing in hydrogen and oxygen upon the desorption efficiency were determined. On the basis of the results obtained it is concluded that optimum results would be obtained by the use of materials which are gas-free and on which tightly bound layers are formed from the ambient atmosphere.