This Data Item presents a method for estimating the lift of a user-specified commercial needle-bearing roller mounted on a translating follower or a swinging follower and driven by a disc cam. In addition@ the maximum static and dynamic contact forces and the maximum angular velocity of the roller are determined and compared with their respective limiting values. The procedure involves calculation of the force acting on the roller due to follower system inertia@ externally applied loads and the action of the return spring. This force@ together with the angular velocity of the roller@ is determined at regular intervals during one rotation of the cam. A Fortran computer program (ESDUpac A9126) that performs all the necessary calculations is provided with this Data Item. Also provided is a Windows executable interface program (VIEWpac W9126) that contains the Fortran code and allows the program to be run in a user friendly manner. The program contains an option allowing the user to determine suitable values of spring rate and preload to ensure that contact between cam and follower in maintained at all times. The Item includes a full description of the mathematical model on which the calculation is based together with guidance on the use of the program@ including interpretation of the output. Three examples illustrating the use of the program in realistic design situations are presented.