  We estimate the dipole of the diffuse 1.5 keV X-ray background from the ROSAT
all-sky survey map of Snowden et al (1995). We first subtract the diffuse
Galactic emission by fitting to the data an exponential scale height, finite
radius, disk model. We further exclude regions of low galactic latitudes, of
local X-ray emission (eg the North Polar Spur) and model them using two
different methods. We find that the ROSAT X-ray background (XRB) dipole points
towards $(l,b) ~ (288, 25) \pm 19 degrees within 30 degrees of the CMB dipole.
Its direction is also in good agreement with the HEAO1 X-ray dipole at harder
energies. The normalised amplitude of the ROSAT XRB dipole is about 1.7 per
cent. Subtracting from the ROSAT map the expected X-ray background dipole due
to the reflex motion of the observer with respect to the cosmic rest frame
(Compton-Geting effect) we find the large-scale dipole of the X-ray emitting
extragalactic sources having an amplitude 90% of the total XRB, in general
agreement with the predictions of Lahav et al (1997). We finally estimate that
the Virgo cluster is responsible for about 20 per cent of the total measured
XRB dipole amplitude.
