ads paper deals with the dynamic characteristics of joints subjected to loading in the direction normal to the joint interface. Experimental results are provided for a variety of joints having different surface topographies. The viscosity of lubricant is shown to have a marked effect upon both the dynamic stiffness and damping of joints. The mechanism of the action of the lubricant layer is discussed and it has been shown that the behaviour of a lubricated joint could be explained in terms of the oil trapped inside both the fully and partially locked oil pockets within the joint interface.