  The Hartle-Thorne metric is an exact solution of vacuum Einstein field
equations that describes the exterior of any slowly and rigidly rotating,
stationary and axially symmetric body. The metric is given with accuracy up to
the second order terms in the body's angular momentum, and first order in its
quadrupole moment. We give, with the same accuracy, analytic formulae for
circular geodesics in the Hartle-Thorne metrics. They describe angular
velocity, angular momentum, energy, epicyclic frequencies, shear, vorticity and
Fermi-Walker precession. These quantities are relevant to several astrophysical
phenomena, in particular to the observed high frequency, kilohertz Quasi
Periodic Oscillations (kHz QPOs) in the X-ray luminosity from black hole and
neutron star sources. It is believed that kHz QPO data may be used to test the
strong field regime of Einstein's general relativity, and the physics of
super-dense matter of which neutron stars are made of.
