Heats of formation have been determined for the tin-oxygen compounds SnO, SnO2, H2SnO, and H3SnOH by ab initio computations of reaction energies for isogyric reactions. The electronic structure methods employed include the coupled-cluster singles and doubles method with a perturbative correction for connected triple substitutions [CCSD(T)] and the Brueckner doubles method with analogous corrections for triple and quadruple substitutions [BD(TQ)]. Correlation-consistent triple- and quadruple-zeta basis sets were employed in conjunction with a large-core pseudopotential and a core polarization potential for Sn, and a basis set incompleteness correction was computed from extrapolations to the infinite basis set limit. Values of 9 4, 10 4, 34 4, and -20 +/- 4 kcal mol(-1) are proposed for DeltaH(f,0)degrees for SnO, SnO2, H2SnO, and H3SnOH, respectively. Polynomial fits were carried out for the heat capacity and the standard enthalpy and entropy over the 300-3100 K temperature range.