The merit of reduction-in-area as a criterion of quality in metals is shown to lie in its influence on breaking stress, but the virtue of elongation is not easy to find. In order to assess the value of elongation, either as a measure of quality or as a guide to design, it will be necessary to separate the overall deformation occurring in tension tests from the localized deformation associated with localized reduction in area. The obstacles to a successful solution of this problem have been shown to be more formidable than- is generally appreciated, and a new solution to the problem has been suggested. This solution involves a device by which an electric circuit is broken when the particular value of strain is reached that is to be taken as the point of separation between general and localized deformation. The report presents results from a number of tests on both low-carbon and alloy steels . These results indicate that the selected criterion of separation is accurately identified by the proposed method; that it gives a satisfactory compromise between too much localized deformation on the one hand, and too little general deformation on the other; and that it is simply and practicably applicable to routine tests.