Phase contrast X-ray imaging is a powerful technique for the detection of low contrast details in weakly absorbing materials. The phase contrast technique is based on the observation of the interference pattern between diffracted and undiffracted waves produced by spatial variations of the real part of the refractive index. Several research groups are exploring ways of exploiting phase effects as a source of image contrast. These approaches fall into three broad categories: interferometry, diffractometry, and phase contrast radiography (or in-line holography). Importantly, a monochromatic beam is not necessary – spatial coherence is much more important than spectral coherence. On this basis, successful applications of unmonochromatic synchrotron hard X-rays to real systems have been implemented by several groups.