Concrete will be the key material for Mankind to create the built environment of the next millennium. The requirements of this infrastructure will be both demanding, in terms of technical performance and economy, and yet be greatly varied, from architectural masterpieces to the simplest of utilities. Role of interfaces in concrete forms the Proceedings of the one day International Seminar held during the Congress, Creating with Concrete, 6-10 Spetember 1999, organised by the Concrete Technology unit, Univeristy of Dundee. It deals with the role of interfaces in the prediction of durability and their effects on concrete characteristics and composite action. The themes of the seminar were Basic Mechanisms and achieving performance.