Abstract
Anisotropic magnetic critical fields Hc2 are calculated for anisotropic Fermi surface (FS) models by use of mean field theory in the clean limit. The Hohenberg-Werthamer theory is applied numerically for selected FS pieces and Matsubara frequencies. The results are compared with experimental results on various anisotropic materials, in particular organic superconductors. It is proposed that the anomalous behaviour of Hc2(T) curves originates from the combination of anisotropy and multiband features