High-temperature water was examined as a medium for the decomposition of highly energetic materials. To this end, a series of aromatic nitroamine compounds was used to mimic the chemical and structural aspects of several important explosives. The compounds 2-nitroaniline (2NA), 4-nitroaniline (4NA), 2,6-dinitroaniline (2,6-DNA), 2-nitro-1,4-phenylene diamine (2NPDA), 2-nitro-1,2-phenylene diamine (3NPDA), and 4-nitro-1,2-phenylene diamine (4NPDA) were chosen to probe the basic structure-reactivity relationships between the number of NO2 and NH2 substituents and their relative locations on the aromatic ring. These experiments revealed that pyrolysis and hydrothermal reaction occurred in parallel, with both rates and selectivities dependent upon the presence of water. Reaction rates were generally higher during reaction in high-temperature water than in neat pyrolysis. The rates of both pyrolysis and hydrothermal reactions increased with increasing number of substituent groups. Finally, the rate of pyrolysis and hydrothermal reaction was lower when nitro and amine groups were adjacent.