Abstract: In this paper, the strength behavior of shale and especially the effect of lamination orientation on its strength have been investigated on the basis of a large quantity of data from uni and tri axial compression tests. The applicability of various strength criteria proposed by different investigators was examined for the tested shale by the comparison of theoretical and measured strength. A simple criterion has been suggested for such shale according to its features, in which parameters can be obtained only from uniaxial test and a couple of triaxial tests.