The screw theory is applied to the study of the instantaneous kinematics of multi-loop mechanisms. A general procedure for investigating the instantaneous kinematics of multi-loop mechanisms is introduced using only better interpretation and implementation of the two fundamental laws of instantaneous kinematics; series and parallel laws. The procedure is applicable to any mechanism specially to that type of practical mechanisms with pre-specified actuated joints. It neither requires special cases to be identified nor requires any more laws to be introduced. Numerical example is presented.