Improving the thermomechanical properties of oxide ceramic reinforcing fibres by means of doping, seeding and sintering additives, Ceramic composite materials, such as CMCs for high-temperature applications, are playing an increasingly important role in the development of future technologies. CMCs made from oxide ceramic fibres offer optimum properties for this, such as low density combined with high mechanical and chemical stability, even at temperatures above 1.000 °C. However, the development and production of oxide ceramic fibres with good mechanical properties is still a major challenge. The lecture will present the latest developments of Fraunhofer ISC/Centre HTL in the field of oxide ceramic fibres for use in high-temperature processes. The focus is on corundum and mullite reinforcing fibres as well as novel fibre compositions through additives and seedings for mullite or corundum, for example yttrium aluminium garnet and zirconium oxide, and the comprehensive analysis of their properties.