When an analysis of the 3-D crack behavior in LEFM is performed, usually only the first term of the Williams series expansion, which corresponds to the r-12 singularity, is taken into account. However, it is well known that t ij stresses (second order terms) have still influence. Even when the t ij stresses are introduced, the only term usually taken into account corresponds to the t 11 factor, generally called T-stress. If a correct 3-D description has to be done, the t 33 term has also to be considered. In this work, the relevance of the t 33 stress term in the analysis of a mode I corner crack is shown in contrast to other approaches that use certain ad hoc parameters, such as the so called T z -constraint factor proposed by Guo and co-workers. The analysis is carried out for elliptical corner cracks with different aspect ratios, showing that the introduction of the t 33 description avoids the approximations inherent to the T z approach.