The experimental results from photoelectron spectroscopy yielding detailed information on interactions of H- and NH2- with one and two molecules of NH3 are supplemented by theoretical studies. The structure of complex anions involved has been determined and the nature of their interactions has been discussed. Electron affinities, dissociation energies, and basicity of H-(NH3)(n) and NH2-(NH3)(n) (n = 1,2) anions have been calculated for theoretically determined structures. The excellent agreement between experimental and theoretical results confirms conclusions derived from experimental studies. A recently proposed complete basis set method has been proven to be a useful tool to study weak molecular complexes.