Abstract: Two grades of armour ceramic have been subjected to high velocity impact by small steel spheres. The depth of penetration, crack formation and the extent of comminution have been characterised. In particular the formation of the Hertzian-type conical fractures has been analysed and compared with other experimental results. A ranking method has been employed which calculates the relative mass advantage of using a ceramic over an aluminium material. It is found that, for this experimental programme, using a harder alumina of lower fracture toughness provides better protection than that given by a softer, tougher grade. However, the advantage of using this ceramic diminishes as the impact velocity is increased. This paper will be interest to the armourer who is concerned with high explosive fragmenting ammunition.