The new equiatomic nickel germanides MgNiGe, SrNiGe, and BaNiGe have been synthesized from the elements in sealed tantalum tubes using a high-frequency furnace. The compounds were investigated by X-ray diffraction both on powders and single crystals. MgNiGe crystallizes with TiNiSi-type structure, space group Pnma, Z = 4, a = 6.4742(2) angstrom, b = 4.0716(1) angstrom, c = 6.9426(2) angstrom, wR(2) = 0.033, 305 F-2 values, 20 variable parameters. SrNiGe and BaNiGe are isotypic and crystallize with anti-SnFCI-type structure (Z = 4, Pnma) with a = 5.727(1) angstrom, b = 4.174(1) angstrom, c = 11.400(3) angstrom, wR(2) = 0.078, 354 F-2 values, 20 variable parameters for SrNiGe, and a = 5.969(4) angstrom, b = 4.195(1) angstrom, c = 11.993(5) angstrom, wR(2) 0.048, 393 F-2 values, 20 variable parameters for BaNiGe. The increase of the cation size leads to a reduction of the dimensionality of the [NiGe] polyanions. In the MgNiGe structure the nickel and germanium atoms build a (3)(infinity)[NiGe] network with magnesium atoms in the channels. In SrNiGe and BaNiGe the (1)(infinity)[NiGe] ribbons are separated by strontium/barium atoms, whereas in the known CaNiGe structure the ribbons are fused to two-dimmensional atom slabs. The crystal chemistry and chemical bonding in AeNiGe (Ae = Mg, Ca, Sr, Ba) are discussed. The experimental results are reconciled with electronic structure calculations performed using the tight-binding linear muffin-tin orbital (TB-LMTO-ASA) method.