Mo-Si-B-based alloys represent perspective materiales for high temperature applications primarily due to their excellent mechanical properties. The decisive shortcoming of these materials is their poor oxidation resistance at intermediate temperatures. It was found that the macroalloying with Ti leads to a substitution of the Mo3Si phase exhibiting poor oxidation resistance by the (Mo,Ti)5Si3 phase showing excellent oxidation behaviour in a wide temperature range. The improved oxidation resistance can be attributed to the formation of a duplex layer consisting of a silica matrix with embedded TiO2 particles. Based on thermodynamic calculations, it was found that the formation of the (Mo,Ti)5Si3 phase can be stabilized by the addition of 2 at.% Fe that causes a widening of the composition region that comprises the required phases, i.e. Mo(ss), Mo5SiB2 and (Mo,Ti)5Si3. Moreover, recent experimental results reveal that the B-doped two-phase Mo-Si-Ti alloys possess high oxidation resistance at both, moderate and high temperatures.