Optical systems for extreme ultraviolet (EUV) lithography require optical elements with wavefront aberrations limited to a fraction of an EUV wavelength to achieve diffraction-limited performance. Achieving wavefront and surface figure metrology at this level of accuracy is one of the key challenges in the development of EUV lithography. We have successfully built and operated a prototype EUV point diffraction interferometer which is capable of performing wavefront measurement of EUV optical elements at their operational wavelength. Initial experiments to characterize the interferometer, and to measure the optical wavefront diffracted from a Fresnel zone plate lens are discussed.