X-ray tomographic microscopy (XTM), a high resolution variant of industrial computed tomography, provides nondestructive, high-resolution “sectioning” of samples and allows three-dimensional mapping of X-ray absorptivity multiple times during an in-situ experiment on a single sample. The capabilities of XTM for damage accumulation studies in composites are described in this paper, with emphasis on what can be accomplished using monochromatic synchrotron radiation. Results are shown for five continuous-fiber metal matrix composites (MMC) (aligned SiC/Al, [02/±45]s SiC/Al, aligned SiC/Ti3Al, aligned SiC/Ti-6Al-4V, and aligned Al2O3/NiAl). The samples' cross-sectional dimensions are approximately 1.5 by 1.5 mm or smaller, and the variation of X-ray absorptivity is measured within each (5.6-μm)3 volume element of the volume studied. An experimental approach for nondestructively quantifying damage evolution with XTM is outlined, and preliminary results are presented for the aligned-fiber SiC/Al MMC. Also discussed are the prospects for improved spatial resolution with XTM and for examining specimens under applied loads and/or with dimensions larger than the current 2 or 3 mm.