FOX-12, or N-guanylurea-dinitramide, is a novel energetic material with low sensitivity and good potential for use as a propellant or insensitive munitions (IM) explosive. This paper reports its synthesis, sensitivity (friction and drop weight), thermal stability and explosion temperature, as well as its bulk crystal density, rho = 1.7545 g/cm(3) (powder X-ray), and its heat of formation, DeltaH(f)(o) = -355 kJ/mol (bomb calorimetry). The activation energy (E-a = 277 kJ/mol) was measured with a differential scanning calorimeter DSC). The ignition temperature was measured using Wood's metal bath (T-ign = 192 degreesC). Using a thermo-chemical code (Cheetah 1.40) and the experimentally determined values of density and heat of formation, the performance was estimated.