An experimental study on the application of the digital image correlation (DIC) technique to measure the deformation of rotating helicopter blades is described. Measurements on two different rotors of diameter 24 and 39 in., with different rotor hubs, were carried out to explore applicability of the technique over a range of scales. Commercial DIC software was synchronized with the frequency of rotation such that rotor blade images could be obtained at a constant rotor azimuth. Bending and torsion mode shapes were extracted from the data with deformation as high as 0.4 in. measured with an accuracy of 0.0038 in. This technique is very advantageous because it is noncontact, cost effective, accurate and simple to implement while yielding full-field, three-dimensional data with a high spatial resolution.