A CRITERION FOR FAILURE OF CONCRETE UNDER COMBINED STRESSES HAS BEEN STUDIED BY TESTING CONCRETE CUBES TO FAILURE UNDER BIAXIAL COMPRESSION. FROM THE RESULTS OF THESE TESTS, CORRELATIONS BETWEEN THE OCTAHEDRAL NORMAL AND SHEAR STRESSES AND THE PRINCIPAL STRESSES IN DIMENSIONLESS FORM WERE OBTAINED. IT WAS FOUND THAT A CRITERION OF FAILURE BASED ON THE PRINCIPAL STRESSES IS MORE USEFUL FOR PRACTICAL PURPOSES. SIMILAR RESULTS WERE OBTAINED FOR CEMENT MORTAR. THE FAILURE CRITERION FOR CONCRETE UNDER TENSILE AND COMPRESSIVE STRESSES IS ALSO DISCUSSED. A DISCUSSION OF THIS PAPER BY K.T.S.R. IYENGAR, K. CHANDRASHEKHARA AND K.T. KRISNASWAMY, APPEARED IN AM CONCR INST J & PROC, VOL62, NO9, SEP 1965, PP1187-96, 2PHOT, 4 FIG, 10 REF. /RRL/A/