  We have developed a numerical code to study the deformation ($\varepsilon =
(I_{zz}-I_{xx})/I_{zz}$, where $I_{ii}$ are the moments of inertia) of neutron
stars in rapidly rotation in a fully general relativistic calculation. We have
found that the deformation is larger, depending on the angular velocity, than
is generally assumed for gravitational wave estimations. Calculations were
performed by employing the Bethe-Johnson I EOS (equation of state) and a new
set of models by the Frankfurt group including $\Lambda$ hyperons for several
choices of their coupling constants to ordinary nucleons. Possible implications
for gravitational wave searches are briefly discussed.
