This report presents the design of equipment for studying the influence of rapid loading and time at load on the initiation of plastic deformation of metals in tension. The machine consists of a cylinder and piston actuated by a hydro-pneumatic system which permits a load as high as 20000 lb. to be applied to a specimen 0.500 in. in diameter in an interval of 0.005 sec or more. This load or a smaller load can be maintained on the specimen for any desired length of time greater than 0.001 sec. The principle features of the design and operation of the equipment are discussed. The application of the data obtained from tests with this equipment is considered. It is estimated that this equipment would cost around $3500 and would provide very important data on the behavior of metals under dynamic loading which could be applied directly to structures.