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The Voyager 2 encounter with the Neptune system included radio science investigations of the masses and densities of Neptune and Triton, the low-order gravitational harmonics of Neptune, the vertical structures of the atmospheres and ionospheres of Neptune and Triton, the composition of the atmosphere of Neptune, and characteristics of ring material. Demanding experimental requirements were met successfully, and study of the large store of collected data has begun. The initial search of the data revealed no detectable effects of ring material with optical depth τ ≳ 0.01. Preliminary representative results include the following: 1.0243 × 10²⁶ and 2.141 × 10²² kilograms for the masses of Neptune and Triton; 1640 and 2054 kilograms per cubic meter for their respective densities; 1355 ± 7 kilometers, provisionally, for the radius of Triton; and J₂ = 3411 ± 10(×10^-6) and J₄ = -26⁺¹²_-20(× 10^-6) for Neptune's gravity …