The Water-Urea-Ammonium Sulfamate ternary system was investigated by means of experimental methods and thermodynamic modelling. Experimental part of the work includes (i) DSC measurements of liquidus and solidus of the Urea-Ammonium Sulfamate, the Water-Ammonium Sulfamate subsystems with the estimation of eutectic point position and a set of experiments on the phase boundaries in the ternary system; (ii) vapor pressure measurements in the binary Water-Ammonium Sulfamate and ternary Water-Ammonium Sulfamate-Urea systems at 298.15 K in a wide concentration range. Excess Gibbs energies of the Water-Ammonium Sulfamate-Urea system and its binary subsystems were described by the Pitzer-Simonson-Clegg model which is reduced to polynomial formalism in case of nonelectrolyte systems. Results of the Water-Urea subsystem reassessment are given. (C) 2016 Elsevier B.V. All rights reserved.