First Observation Of The Rare Decay Mode K-L(0)-> E(+)E(-)

In an experiment designed to search for and study very rare two-body decay modes of the K-L(0), we have observed four examples of the decay K-L(0) --> e(+)e(-), where the expected background is 0.17 +/- 0.10 events. This observation translates into a branching fraction of 8.7(-4.1)(+5.7) x 10(-12), consistent with recent theoretical predictions. This result represents by far the smallest branching fraction yet measured in particle physics. [S0031-9007(98)07665-0].