A review is given of the techniques that have been used in the construction of dynamic tension-testing machines. The problems involved in obtaining reliable tensile stress-strain curves at high strain rates are discussed. A new apparatus, designed to give accurate stress-strain curves in tension at strain rates of the order of 1000 per second, is then described. The theoretical basis of the test method is indicated, and some experimental results obtained with the apparatus are presented, both for materials that exhibit a definite yield point and for those that do not.