The use of mineral admixtures in concrete is well accepted today. Though there are several methods for the design of normal concretes of a specified strength grade, the design of concretes containing the newer mineral admixtures like metakaolin is not yet well understood. Also the information available on the behaviour of metakaolin in concrete is very little. This paper is directed towards an understanding of the strength behaviour of concretes containing metakaolin, through a systematic evaluation of the most recent information available. These evaluations are based on the efficiency concepts that were successfully utilized earlier by the author for other pozzolans like fly ash, silica fume, blast furnace slag etc. It was observed that metakaolin is a high efficiency pozzolan and can exhibit efficiencies comparable to that of silica fume.