The KamLAND experiment measures the oscillation of anti-neutrinos
produced by distant nuclear reactors. I will present new results which
include an almost fourfold increase in the detector exposure and an
analysis of the entire inverse beta decay spectrum above the reaction
threshold. From spectral distortion we find decisive evidence of
neutrino oscillation. I will report a precise value for {\Delta}m^{12}
and stringent constraints on \theta_{12}, the oscillation parameters
relevant for both reactor and solar neutrinos. Combining the KamLAND
and solar neutrino experiment results give the current best measure of
neutrino oscillation parameters.