[en] We discuss experimental and theoretical results which probe the identity, characteristics and thermodynamics of interstitial hydrogen storage sites in amorphous transition metal alloys. Utilizing experimental findings which describe both the local nature of hydrogen interstitial site properties and the thermodynamics of these sites, we emphasize the development of site statistical models to explain these observations. Recent models provide detailed methods for calculating hydrogen site binding energies and for predicting thermodynamic properties such as pressure-composition isotherms. (author) 36 refs., 9 figs