Work carried out on Nicalon/glass composites as part of a larger programme on the structure and properties of ceramic-matrix composites is described and is in contrast to publications by this group on related materials in which the interfacial bonding was quite different. As a consequence of differences in manufacturing, the interfacial bonding in these more recent materials is substantially improved, as demonstrated by the markedly improved level of shear stiffness (by a factor of 2-3) and the higher level of interlaminar shear strength (some 50%-100% improvement). There is, however, an accompanying deterioration in the tensile and flexural strengths. The fracture mode of these Nicalon/borosilicate-glass composites is strongly influenced by the cristobalite content and the properties of the interface, both of which are controlled to a large extent by the manufacturing parameters.