A technique is presented in which approximate values of the elongation stress can be measured at large elongation rates by using opposed orifices to generate a stagnation flow similar to uniaxial elongation. The elongation rate is related to the volumetric flow rate of fluid into the orifices and the apparatus geometry. The first law of thermodynamics is simplified to relate the pressure drop due to fluid entering the orifices with the first normal stress difference in uniaxial, elongation flow. Thus only the flow rate and pressure drop are needed to determine the elongation viscosity as a function of elongation rate. Results for elongation rates up to 1000 s−1for three polymer melts, linear low‐density polyethylene, low‐density polyethylene, and polypropylene, are presented. The technique can also be used at low elongation rates and results are presented in which the elongation viscosity approaches 3× the zero shear viscosity.