Holography with high energy x-rays is now feasible due to the coherence properties of third generation synchrotron sources. Simple in-line holographic techniques can be used to generate edge-enhanced images which for many samples can be interpreted without direct phase retrieval. The coherence properties of such sources and their exploitation for phase-contrast microimaging are demonstrated. The technique can easily be combined with computed microtomography (CMT) data collection and reconstruction strategies for three-dimensional imaging. A dramatically improved image contrast, as compared with absorption CMT, was obtained when imaging a wet human coronary artery specimen. In the tomograms, previously invisible detail could be visualized with absorbed doses below the level where radiation damage impedes the imaging. The results indicate the considerable potential of the in-line holographic CMT method in three-dimensional biomedical microscopy.