Ab initio calculations of the structures and energies of the mono-, di-, and trinitrosamides are compared to mono-, di-, and trinitramides. Highly accurate standard heats of formation of this series of nitramides and nitrosamides are calculated using isodesmic reactions and high-level theories. The nitrosamides have heats of formation at 0 K that are 20-40 kcal/mol higher than the analogous nitramides. The N-N bond strengths are comparable whether a NO or NO2 group is bonded to the central nitrogen atom. The data suggest that converting the nitro groups to nitroso groups will-result in compounds that have lower weight, shorter N-N bond lengths, and higher energy content, at the expense of lower oxygen balance. This suggests that nitrosamides are potentially useful high-energy materials. A revised ΔHf° for NH2NO2 is proposed to be 3.8 kcal/mol at 0 K, in close agreement with previous theory and very different from experiment. Recommended values for ΔHf° are 34 and 71 kcal/mol for di- and trinitramide, respectively, and 22, 65, and 112 kcal/mol for mono-, di- and trinitrosamide, respectively. The errors in the monosubstituted molecules are estimated at 1 kcal/mol, and the errors are estimated at ±2 and ±3 kcal/mol for the di- and trisubstituted molecules, respectively. Nitrosamides have bond strengths comparable to those of the nitramides. © 1999 American Chemical Society.