The purpose of this thesis is to determine the effect mechanical prestressing (cold working) of a centrally located hole in a finite width plate has on the allowable working stress level of the plate under applied tension loads. Mechanical prestressing, as utilized in this investigation, consists of forcing an oversize mandrel through the hole which causes yielding of the material near the hole thus producing permanent set of the hole boundary and leaving an internal (residual) stress field in the plate. The major portion of this study consists of the experimental determination of these residual stresses and the resulting stress pattern after the application of an applied tension load. This stress pattern is compared with the stress pattern for the· same configuration without any hole prestressing in order to exhibit the change in the allowable working stress level. A comparison of stress concentration factors is made. In addition, both the Mises-Hencky and' the Tresca yield theories are utilized to obtain theoretical residual stress distributions which are compared with those obtained from the experimental test.