N,N-Dimethylaminoxygermane, H3GeONMe2, was prepared by the reaction of H3GeBr with LiONMe2 in dimethyl ether at -96 degreesC. The identity of H3GeONMe2 was proven by gas-phase IR and solution NMR spectroscopy (H-1, C-13, N-15, O-17). It is unstable volatile liquid compound. It decomposes by cleavage of a Ge-O and a Ge-H bond giving HONMe2 and an insoluble germanium hydride polymer (GeH2)(n). This decomposition reaction has been modeled at the MP2/6-311G(d,p) level of theory by the homodesmotic reaction H3GeONMe2 + Ge2H6 --> Ge3H8 + HONMe2, which is predicted slightly exothermic by 14 kJ mol(-1). The molecular structure of H3GeONMe2 was determined by gas-phase electron diffraction supported by an ab initio geometry [MP2/6-311G(d,p)] and a force field [MP2/6-31G(d)]. The structure of the compound in the crystal lattice was determined by low-temperature crystallography using a single crystal of H3GeONMe2 grown in situ [C2H9NOGe, orthorhombic, Pnma, Z = 4, a = 8.1280(12) Angstrom, b = 9.7037(15) Angstrom, c = 7.0722(12) Angstrom]. Important bond lengths and angles (gas phase/solid state, Angstrom /deg) are Ge-O 1.785(2)/1.815(1), O-N 1.462(7)/1.460(2), N-C 1.460(4)/1.453(2), Ge-O-N 105.2(5)/104.6(1), O-N-C 105.8(5)/105.8(1), C-N-C 110.8(9)/111.2(2), Ge...N 2.587(6)/2.601(1). In the solid state the compound forms infinite chains by intermolecular Ge...O contacts of 2.808 Angstrom. The question of the attraction between Ge and N atoms is discussed with respect to reference Ge/O and N/O compounds, which have wider angles at oxygen than H3GeONMe2. For comparison the structures of the compounds H3CONMe2, H3SiONMe2, and H3SnONMe2 were also calculated to reflect the influence of the group 14 atom on the structure and to discuss the occurrence of weak E...N interactions in the compounds H3EONMe2.