  We calculate the N\'eel temperature $T_N$ for two-dimensional isotropic
dipolar Heisenberg antiferromagnets via linear spin-wave theory and a high
temperature expansion, employing the method of Callen. The theoretical
predictions for $T_N$ for K$_2$MnF$_4$, Rb$_2$MnF$_4$, Rb$_2$MnCl$_4$ and
(CH$_3$NH$_3$)$_2$MnCl$_4$ are in good agreement with the measured values.
