Vibration characteristics of a structure correlate to the distribution of mass, stiffness and damping in the structure. Therefore, a change in any one of these three parameters will result in a change of the vibration characteristics of the structure. It is a fact that a structural damage results in a local reduction of stiffness of the structure and therefore a reduction of the natural frequencies. Methods to detect and possibly localise damage in structures using vibration measurements have been a subject of research interest among the structural dynamics community. The use of a vibration based methodology in detecting and localising damages in big structures like bridges will provide an efficient monitoring and diagnostic tool and overcome accessibility difficulties associated with physical inspection. The paper discusses a methodology proposed for the detecting and localising damage in structures with specific application to structural damage in bridges using vibration data.