The great forward strides that concrete construction has experienced in recent years have been largely due to the use of improved materials. A new development that promises to increase the economy of conventionally reinforced concrete is the application of high strength reinforcement; that is, bars having a yield strength over 50,000 psi. Such high strength reinforcing would mean smaller members, lower costs and more attractive structures. These advantages would be especially important in heavily loaded buildings and bridges. There are two ways of manufacturing high yield point steel. The low cost technique is by a process called cold working. Unfortunately, cold worked steel has an ultimate strength only slightly above its yield point. This means that there isn't much of a safety factor. The other type is called a "naturally hard" steel that owes its great strength to a high carbon content and special alloys. Using the latter process, Swedish steel mills have produced rebars with yield points as high as 100,000 psi. But the naturally hard steels are comparatively expensive. A big hurdle in this country will be the building codes. For the more expensive high strength bars to demonstrate their economic advantages, building codes will have to be modified to permit higher working stresses.