  We have developed a model to describe two-point correlation functions of
clusters of galaxies in X-ray flux-limited surveys. Our model properly takes
account of nonlinear gravitational evolution of mass fluctuations,
redshift-space distortion due to linear peculiar velocity field and to
finger-of-god, cluster abundance and bias evolution on the basis of the Press
-- Schechter theory, the light-cone effect, and the selection function due to
the X-ray flux, temperature and luminosity limits. Applying this model in
representative cosmological models, we have presented quantitative predictions
for X-ray selected samples feasible from the future surveys with the X-ray
satellites including Astro-E, Chandra, and XMM. The comparison of these
predictions and the observed cluster clustering will place important
cosmological constraints which are complementary to the cluster abundance and
the cosmic microwave background.
