Treatment of BeCl2 with dry liquid ND3 and subsequent removal of the solvent leads to the colourless microcrystalline powder of [Be(ND3)(4)]Cl-2. It crystallises in the orthorhombic space group Pna2(1) with a = 9.395(4), b = 11.901(6), c = 6.761(3) angstrom, V = 755.9(6) and Z = 4 at 27 degrees C, and a = 9.3736(8), b = 11.8162(12), c = 6.6596(6) angstrom, V = 737.62(12) and Z = 4 at -269.6 degrees C. The structure contains the tetrahedral tetraammineberyllium(II) cation which follows the octet rule. It was shown to be stable under ambient conditions and temperatures up to approximately 175 degrees C. We additionally discuss the aid of solid-state quantum chemical calculations for the assignment of proper crystallographic space groups in cases where the choice between centrosymmetry and noncentrosymmetry is not completely obvious, e.g. here between Pna2(1) and Pnma. Thermogravimetric measurements show that [Be(ND3)(4)]Cl-2 decomposes only above approximately 175 degrees C, giving off two equivalents of ND3 to form [Be(ND3)(2)Cl-2]. The latter seems to be stable up to approximately 300 degrees C after which it sublimes. These results show unambiguous evidence for the stability of the tetraammineberyllium(II) cations of the title compounds from -269.6 degrees C to 175 degrees C.