I have used Monte Carlo perturbations of synthetic tensors to evaluate the Hext/Jel¿nek elliptical confidence regions for anisotropy of magnetic susceptibility (AMS) eigenvectors. When the perturbations are 33% of the minimum anisotropy, both the shapes and probability densities of the resulting eigenvector distributions agree with the elliptical distributions predicted by the Hext/Jel¿nek equations. When the perturbation size is increased to 100% of the minimum eigenvalue difference, the major axis of the 95% confidence ellipse under estimates the observed eigenvector dispersion by about 10¿. The observed distributions of the principal susceptibilities (eigenvalues) are close to being normal, with standard errors that agree well with the calculated Hext/Jel¿nek errors. The Hext/Jel¿nek ellipses are also able to describe the AMS dispersions due to instrumental noise and provide resonable limits for the AMS dispersions observed in two Hawaiian basaltic dikes. I conclude that the Hext/Jel¿nek method provides a satisfactory description of the errors in AMS data and should be a standard part of any AMS data analysis. ¿ American Geophysical Union 1991