  A general formula for the correlation function in redshift space is derived
in linear theory. The formula simultaneously includes wide-angle effects and
cosmological distortions. The formula is applicable to any pair with arbitrary
angle $\theta$ between lines of sight, and arbitrary redshifts, $z_1$, $z_2$,
which are not necessarily small. The effects of the spatial curvature both on
geometry and on fluctuation spectrum are properly taken into account, and thus
our formula holds in a Friedman-Lema\^{\i}tre universe with arbitrary
cosmological parameters $\Omega_0$ and $\lambda_0$. We illustrate the pattern
of the resulting correlation function with several models, and also show that
validity region of the conventional distant observer approximation is $\theta
\le 10^\circ$.
