This work examined the reaction pathways involved in the initial decomposition of aqueous hydroxylamine solutions via the overall reaction, 2NH2OH -> NH3 + HNO + H2O, using quantum chemistry calculations incorporating solvent effects. Several possible decomposition mechanisms were identified and investigated: three neutralneutral bimolecular, two water-catalyzed, one neutral trimolecular, two ion-neutral bimolecular, and one cation-catalyzed. Optimized structures for the reactants, products, and transition states were obtained at the omega B97XD/6-311++G(d,p)/SCRF = (solvent = water) level of theory, and the total electron energies of such structures were calculated at the CBS-QB3 level of theory. The cation-catalyzed reaction 2NH2OH + NH3OH+ -> NH4+ + HNO + H2O + NH2OH (maximum energy barrier (triangle E-0(double dagger)) = 53.6 kJ/mol) and the anion-neutral bimolecular reaction NH2OH + NH2O- -> NH3 + (NO-)-N-1 + H2O (triangle E-0(double dagger) = 79.0 kJ/mol) were both found to be plausible candidates for the dominant step in the initial decomposition. The results of this study indicate that both acidic and basic conditions can affect the thermal stability of hydroxylamine in water.