The high-temperature creep and flexural deformation of a model alumina-glass ceramic is reported over the temperature range in which the glass phase softens (from a viscosity of ~107 to ~103 P). Under both loading conditions the deformation is accompanied by extensive cavitational damage throughout the material. The cavitation is inhomogeneously distributed and at high stresses can be localized into bands. In addition, crack propagation at high temperature results in the formation of a cavitational zone on either side of the fracture and measurements of its size are presented as a function of deformation temperature. On the basis of the microstructural observations of the deformed material, the sequence by which isolated cavities grow and link up prior to failure, is described. © 1985 Chapman and Hall Ltd.