  We investigate the effects of a nonzero leptonic mixing angle $\theta_{13}$
on the solar neutrino day-night asymmetry. Using a constant matter density
profile for the Earth and well-motivated approximations, we derive analytical
expressions for the $\nu_e$ survival probabilities for solar neutrinos arriving
directly at the detector and for solar neutrinos which have passed through the
Earth. Furthermore, we numerically study the effects of a non-zero
$\theta_{13}$ on the day-night asymmetry at detectors and find that they are
small. Finally, we show that if the uncertainties in the parameters
$\theta_{12}$ and $\Delta m^2$ as well as the uncertainty in the day-night
asymmetry itself were much smaller than they are today, this effect could, in
principle, be used to determine $\theta_{13}$.
