One‐dimensional compression measurements have been made on samples of natural rubber gum stock. The experimental stress‐strain curve and the theoretical relationf=G(L−1/L2) agreed quite well over the entire range (0%–32%) studied. No hysteresis loop was evident.The friction at the faces of the sample was eliminated by a new method of lubrication. The sample essentially floated between two thin films of a liquid which flowed under pressure between the sample and compressing plates allowing uniform lateral expansion of the sample.