[en] The weak-neutral-current reaction upsilon-bar/sub e/ + d → n + p + upsilon-bar/sub e/ has been observed concurrently with the charged-current process upsilon-bar/sub e/ + d → n + n + e⁺ using an instrumented D₂O target exposed to an upsilon-bar/sub e/ flux of 2.5 x 10¹³ cm^-2sec^-1. The measured neutral-current cross section, (3.8 +- 0.9) x 10^-45 cm²/upsilon-bar/sub e/, is consistent with the Weinberg-Salam model, dependent in this case only on the axial-vector contribution. The charged-current reaction cross section is (1.5 +- 0.4) x 10^-45 cm²/upsilon-bar/sub e/, in fair agreement with expectation