Concentrated contacts in motion are found in most mechanical machines. The elasto-hydrodynamic lubrication (ehl) theory deals with the lubrication of moving concentrated contacts. The first important successful application of ehl was to rolling contact bearings. The theory can today be used by designers for optimizing bearing design and predicting bearing life, power loss, temperature and dynamic behaviour. The application of ehl to gearing is more complicated. The simplified film thickness calculation methods for gears offer a practical way of making a rough estimation of the risk of failure. Methods for calculating the film thickness in the difficult transient contact conditions and along the gear contact have recently been developed. The application of ehl to the transient conditions in a cam and tappet contact is promising but needs more work. To achieve better methods for the design of lubricated concentrated contacts, a better understanding of microgeometry and thermal and chemical effects in the contact is required