The effects of pressure and a partial substitution of Fe by Mn on the intrinsic magnetic proper-ties (saturation magnetization Ms, anisotropy K-1, spin reorientation transition TSR and Curie point Tc) of Fe3Ge single crystal (DO19 hexagonal phase) were investigated. The magnetocrystalline anisotropy of the compound is planar at low temperature and, through a second order spin reorientation transition, it becomes axial above T-SR=373 K. The Mn substitution for Fe widely extends the region of axial anisotropy, shifting TSR down to 126 K in (Fe0.8Mn0.2)(3.25)Ge. However Ms and TC are markedly reduced. In both compounds, high pressure has a little influence on the 3d moment, while it reduces the planar character of the anisotropy.