Tensile strength of specimens of coated fabric which had a crack, a bias crack and a circular defect respectively was measured using a uniaxial and using a biaxial tensile tester. Then, uniaxial and biaxial tensile strength figures were compared, and strengths for the three types of defect condition were compared. Further, uniaxial strengths of four types of coated fabric material specimens with cracks were measured, and the anisotropy of tensile strength along warp and filling was investigated. It was concluded : that strength under uniaxial stress condition was smaller than that under biaxial stress condition; that the crack defect was the most significant type of defect in decreasing strength ; and that the anisotropy of the uniaxial strength of a specimen with a crack depended on differences of type of material and on initial crack length. And, relations between crack opening ratio under deformation and stress were measured on the specimen, where it was discovered that crack opening ratio was approximately linearly proportional to stress magnitude over a limited region of stress magnitude and that this relation was useful for measurement of stress in coated fabrics.