In this work the viscosity of NH4NO3+ formamide solutions in a wide concentration range up to 0.3703 ammonium nitrate mole and in the temperature range from (298.15 to 348.15) K was determined. The validity of JonesDole and GoldsackFranchettos equations were checked and applied to describe the viscosity dependence on concentration. The equation for the viscosity dependence on both the ammonium nitrate mole fraction and temperature is also presented in this paper.