For a wide variety of dentine bonding systems the bond strength before and after thermocycling was determined on dentine with and without hydraulic tubular pressure. The importance of the hydrophillic nature of several bonding systems could be demonstrated. The dentine smear layer could not prevent a negative effect of water in the tubulus on hydrophobic systems. Removal of the smear layer had a positive effect on the durability of the bond. When loaded until fracture, some bonding systems resisted adhesive failure.