Although dynamic shearing properties of rock discontinuities are of great importance in many rock engineering applications, it is very rare to see dynamic shear tests on rock discontinuities. The author describes static, cyclic, one-way and two-ways dynamic shearing experiments on various natural rock discontinuities and saw-cut planes and discusses the shear strength characteristics obtained from the different testing techniques and interrelations. The experiments clearly showed that the dynamic shear behavior of discontinuities are very complex and anisotropic. Nevertheless, this study provides some fundamental understanding on the static and dynamic behavior of rock discontinuities and their correlation with each other.