WE report here some preliminary measurements of the mechanical properties of a new ceramic material. The material - a pure silica matrix reinforced by carbon fibres - has been made in our laboratory as part of a programme aimed at the manufacture of a ceramic material which, although composed of stiff and brittle components, is itself strong and relatively tough. Such a material forms a good test of current theories for improving the toughness of composite materials, and of reinforced ceramics in particular1. © 1969 Nature Publishing Group.