ESDU Struct 02.00.00 gives yielding and failure criteria applying to materials subjected to combined loadings which may be compared to the results obtained from uniaxial tension testing in determining failure for design purposes. For brittle materials which do not yield before failure the principal stress criterion of Rankine is given. For ductile materials, four criteria are suggested: maximum principal strain, maximum shear stress, maximum strain energy and von Mises-Hencky. Comments are included on the relative conservatism of those criteria for ductile materials. It is noted that the use of stresses calculated from an elastic analysis will not be strictly appropriate for yield criteria and that the mechanism of failure under combined loadings is not one of yielding although the use of yield criteria is usually conservative.