A vulcanized natural rubber has been deformed in simple extension and in pure shear and the resulting diminution in X-ray intensity of the "amorphous" halo used as a measure of crystallinity. The effect of mode of deformation and attempts to reach "equilibrium" states by heat treatment at constant deformation are described. The values obtained for simple extension are in accord with those reported by Goppel and not with those of Field. The degree of crystallinity is greater in pure shear than in simple extension at the same principal extension ratio. Corrected values for the orientation of crystalline regions have been obtained and a comparison is made between volume changes and X-ray measurements for simple extension.