The ability to bond restorative materials to each other and to the dental hard tissues is becoming increasingly important in clinical dentistry. By obtaining a micromechanical or chemical bond between restorative materials and tooth tissue, the need for macro-retention is obviated and options for treatment are considerably extended. The spectrum of bonding is now broad, involving the hard tissues enamel and dentine, and the restorative materials metal, porcelain, composite and glass ionomer. This paper deals mainly with the bonding of composite to enamel and dentine.