  Neutral beam injection or ion cyclotron resonance heating induces pressure
anisotropy. The axisymmetric plasma equilibrium code HELENA has been upgraded
to include anisotropy and toroidal flow. With both analytical and numerical
methods, we have studied the determinant factors in anisotropic equilibria and
their impact on flux surfaces, magnetic axis shift, the displacement of
pressures and density contours from flux surface. With $p_\parallel/p_\perp
\approx 1.5$, $p_\perp$ can vary 20% on $s=0.5$ flux surface, in a MAST like
equilibrium. We have also re-evaluated the widely applied approximation to
anisotropy in which $p^*=(p_\parallel + p_\perp)/2$, the average of parallel
and perpendicular pressure, is taken as the approximate isotropic pressure. We
find the reconstructions of the same MAST discharge with $p_\parallel/p_\perp
\approx 1.25$, using isotropic and anisotropic model respectively, to have a 3%
difference in toroidal field but a 66% difference in poloidal current.
