Rolling Element bearings are among the most common elements used in the operation of rotating machines. They are, however, one of the weak points in these machines where a large majority of problems associated are caused by bearing failures. As a result, condition monitoring of the rolling element bearings are important in order to keep these machineries in their proper operating condition. Analysis and maintenance of any rolling element bearings failures are made much easier if any fault can be identified during its early stage. Thus, it is the aim of this book to investigate the relative shaft displacement and bearing housing vibration measurements for the early fault detection in rolling element bearings. Experiments were conducted on a rotor Kit that closely simulates the actual behaviour of rotating machines.