The energy of NS was computed via CCSD(T) theory, together with extrapolation to the complete basis set limit and corrections for anharmonic zero-point energy, scalar and vector relativistic terms, and core-valence electron correlation. The results were employed with three working reactions to find Delta(f)H(0)(NS) = 277.3 +/- 12 kJ mol(-1) and Delta(f)H(298)(NS) = 278.0 +/- 2 kJ mol(-1). This thermochemistry is consistent with, but much more precise than, earlier literature values. (C) 2002 Elsevier Science B.V. All rights reserved.