Combined measurements of the photoelectromagnetic effect and photoconductivity in three different geometries can be used to determine the anisotropy factors (&mgr;n∥/&mgr;n⊥, &mgr;p∥/&mgr;p∥) and the mobility ratios (&mgr;n∥/&mgr;p∥, &mgr;n⊥/&mgr;p⊥) in anisotropic semiconductors. In the present work this method has been applied to mercuric iodide; previous data on electron mobilities are confirmed, whereas the hole mobility is nearly isotropic.