In SiC-SCS-6-fibre-reinforced IMI834 alloys, a high thermal stability of tensile properties and of the fibre-matrix interface for temperatures up to 700 degrees C was reported. In the present paper, the interface of these composites is investigated by analytical transmission. electron microscopy in the as-processed condition and after a thermal treatment at 700 degrees C for 2000 h and at 800 degrees C for 500 h. The interface in (SiC-SCS-6)-IMI834 composites consists of two layers : the TIC reaction zone with a thickness of about 0.4 mu m and a layer of a (Ti, Zr)(x)Si-y phase with a thickness of about similar to 0.1 mu m. The energy-dispersive electron beam analysis of the (Ti, Zr)(x)Si-y layer results in a (Ti, Zr)(2)Si phase with a Ti-to-Zr ratio of approximately 1.4. Electron beam diffraction of the (Ti, Zr)(x)Si-y layer identifies it as S2 silicides present in near-alpha alloys. The thermal stability of the interface in the (SiC-SCS-6)-IMI834 composites is ensured by the continuous coating of the (Ti, Zr)(x)Si-y, phase. This is the case for a thermal treatment at temperatures up to 700 degrees C for 2000 h. After the treatment at 800 degrees C for 500 h, the thickness of the TiC reaction zone is increased, gaps in the (Ti, Zr)(x)Si-y layer appear, titanium carbide grows further into the titanium matrix and the thermal stability of the interface is lost.