The investigation discussed in this paper was made to determine the effect of cold-working on the endurance limit and other related physical properties of steel. This cold-working was of a surface nature resulting in an almost negligible reduction in area. The preliminary work conducted in this field, for the most part, has been a laboratory development in so far as the technical and mechanical details of the surface-rolling process is concerned, but it has been sufficient to show the advantageous effect of this process on the endurance limit of steel, thereby justifying further study. Therefore, the investigation discussed in this paper was inaugurated to determine the various factors involved in the immediate application of this surface-rolling process in practice. As a result this paper is in the nature of a progress report covering principally tests made on 0.3-in, and 1-in. diameter cold-worked specimens without stress concentration. Further fatigue tests are being conducted on 1-in. and 2-in. diameter surface-rolled specimens with and without stress concentration and on 0.080-in. diameter fatigue specimens machined from various layers of 2-in. diameter surface-rolled specimens.