The fracture strength of a melt-infiltrated SiC-mullite composite was measured from room temperature to 1500degreesC using a three-point bending test. The strength under argon at atmospheric pressure was not high. Mullite decomposition was found to be severe even at 1100degreesC in a reducing atmosphere, thus significantly degrading its strength. The strength in air, where the decomposition was suppressed, was moderately high and retained up to 1100degreesC. The composite revealed typical brittle failure up to the highest investigated temperature of 1500degreesC, with an indication of failure by slow crack growth at high temperature. (C) 2004 Kluwer Academic Publishers.