In this paper the dynamics of joint motion and the systems of joint reaction forces are investigated in flexible-link robots with rotational and translational joints. Some new concepts are introduced concerning the kinematic and dynamic modeling of flexible links. The dynamic equations for the joint motions and for the systems of reaction forces are derived by using the Newton-Euler laws. The effects of joint friction are discussed. The formulation is applicable for large flexible displacements as well. The determination of bearing reaction forces is studied.