A nondestructive evaluation procedure is presented for identifying a crack in a structure using modal test data. The structure is discretized into a set of elements and the crack is assumed to be located within one of the elements. Measured vibration frequencies and mode shapes are used in an identification process to identify the cracked element based on a simple reduced stiffness model. Static deflection analyses of the structure with and without a crack are performed and a strain energy equilibrium equation is constructed for determining the size of the crack. The detection of a crack on a damaged beam is used to illustrate the applications of the proposed procedure. The present procedure is general and can be easily extended to complex structures with multiple cracks.