  The main goal of the KamLAND reactor electron anti-neutrino experiment is a
search for electron anti-neutrino oscillation using inverse-beta decay reaction
in 1,000 ton of ultra-pure liquid scintillator. The data-set is 1490.8 days
from Mar. 2002 to May 2007. The best-fit oscillation parameters are Delta
m^{2}_{21} = 7.58^{+0.14}_{-0.13} (stat.) +/- 0.15 (syst.) x 10$^{-5} eV^{2}
and tan^{2}theta_{12} = 0.56^{+0.10}_{-0.07} (stat.) ^{+0.10}_{-0.06} (syst.).
The statistical significance for reactor electron anti-neutrino disappearance
is 8.8 sigma, and an undistorted electron anti-neutrino energy spectrum is
disfavored at > 5 sigma.
