  We study how well KamLAND, the first terrestrial neutrino experiment capable
of addressing the solar neutrino problem, will perform in ascertaining whether
or not the large mixing angle MSW solution (with $10^{-5}<\Delta m_{21}^2<
10^{-4} eV^2$ and oscillation amplitude $sin^2 2 \theta_{12}>0.3$) is correct.
We find that in a year of operation KamLAND will provide unequivocal evidence
for or against this solution. Furthermore, its sensitivity to the
three-neutrino oscillation parameters in this region is sufficiently acute as
to determine $\Delta m_{21}^2$ to approximately $\pm 10$ % (for $sin^2 2
\theta_{12}>0.7$) and to fix $sin^2 2 \theta_{12}$ to within $\pm 0.1$ (at the
$2\sigma$ level) with three years of accumulated data, independent of the value
of $\theta_{13}$.
