The effects of various additions of GeO2or SnO2, in a Mn-Zn ferrite on the microstructure and magnetic properties have been studied. The behavior of GeO2additive has been found to be similar to that of SiO2. Up to a GeO2content of 0.64 mol%, the magnetic properties improve through the increase in the density. At a higher GeO2content of 1.28 mol%, the properties deteriorate due to the occurrence of discontinuous grain growth. Further addition of GeO2gives better grain structure but poor properties. The presented results suggest that Ge4+dissolves in the ferrite to a very limited extent and GeO2exists as a second phase. SnO2, on the other hand, has been found to be soluble in the ferrite and does not alter the microstructure even up to a content of 5.70 mol%. The essential property of this additive is found to be in its ability to modify the variation of μiwith temperature without deteriorating the μiand core losses. The temperature variation of the bulk resistivity has also been studied.