  We present the first detection of orbital motion in the cataclysmic variable
EX Hydrae based on X-ray data from the Chandra X-ray Observatory. The large
collecting area of the telescope and the high resolution of the HETG
spectrometers allow for an unprecedented velocity accuracy of ~15 km/s in the
X-ray wavelength regime. We find an emission line velocity amplitude of
58.2+-3.7 km/s and infer a white dwarf mass of 0.49+-0.13 M_sun, in good
agreement with previous studies using optical, ultraviolet, and far ultraviolet
data.
