[en] The UPSILON' state has been observed as a narrow resonance at M(UPSILON') = 10.02 +- 0.02 GeV in e⁺e^- annihilations, using a NaI and lead-glass detector in the DORIS storage ring at DESY. The ratio GAMMAsub(ee)GAMMAsub(had)/GAMMAsub(tot) of electronic, hadronic, and total widths has been measured to be 0.32 +- 0.13 keV. The parameters of the UPSILON particle have also been determined to be M(UPSILON) = 9.46 +- 0.01 and GAMMAsub(ee)GAMMAsub(had)/GAMMAsub(tot) = 1.04 +- 0.28 keV. The mass difference is M(UPSILON')-M(UPSILON)=0.56 +- 0.01 GeV. (Auth.)