In this study, the empirical relationships proposed in the current literature were verified to assess their validity for compressive strengths between 66 and 132 MPa (8700 to 19,145 psi). A relationship was suggested to predict the ultimate strength 4 very high-strength concrete under triaxial compression. Furthermore, strength criteria essentially developed to estimate the ultimate strength of intact rock were applied to the concrete. The results of triaxial tests were employed to verify the applicability of these strength criteria for high-strength concrete. It is interesting to note that the strength criteria developed for intact rocks can also be applied to the assessment of ultimate strength and failure curve in high-strength concretes. Knowing only the cylinder compressive strength and the ratio of tensile-to-compressive strength, the failure envelope can be successfully evaluated by means of these criteria without performing triaxial tests in high-strength concretes.