The damage evaluation behaviour of alumina fibre-reinforced mullite ceramic matrix composites subjected to cyclic fatigue was investigated by means of acoustic emission (AE) monitoring and forced resonance techniques. AE technique provided sufficient information about the damage initiation and progression in real time whilst the forced resonance, (FR) technique allowed the detection of changes in elastic modulus (E) and internal friction (Q(-1)) that occurred with increasing number of cyclic fatigue at room temperature. From the two non-destructive detection techniques results combined with microstructural observations, it is concluded that the composite cyclic fatigue damage evolution begins with multiple crack formation within the matrix and is followed by delamination (interfacial failure). Final failure of the composite is caused by fibre fracture and extensive cyclic sliding along the fibre/matrix interface. The strong bonding between mullite matrix and alumina fibre caused by the glassy phase within the mullite matrix determined the fatigue performance of the composite at 1350degreesC. Regions with glassy phase failed catastrophically as a result of early fibre fracture. (C) 2002 Elsevier Science Ltd. All rights reserved.