There are two experimental approaches to determining DeltaH(f0)degrees (OH), which produce values of this key thermodynamic quantity that differ by >0.5 kcal/mol. The apparent uncertainty of the positive ion cycle approach resides in the measurement of the appearance energy of OH+ from H2O, while the uncertainty of the spectroscopic approach resides in the determination of the dissociation energy of OH(A(2)Sigma (+)). In this note we present an independent experimental determination of the appearance energy that confirms the accuracy and enhances the precision of the existing positive ion cycle value for DeltaH(f0)degrees (OH). We also present electronic structure calculations of the OH(A(2)Sigma (+)) potential energy curve. which suggest that the extrapolation method used to obtain the spectroscopic dissociation energy is in error. Finally, we present the largest ab initio electronic structure calculations ever performed for DeltaH(f0)degrees (OH) that have an apparent uncertainty much less than 0.5 kcal/mol and support only the positive ion cycle value. Although all major thermochemical tables recommend a value of DeltaH(f0)degrees (OH) based on the spectroscopic approach, the comet value is that of the positive ion cycle, DeltaH(f0)degrees (OH) = 8.83 +/- 0.09 kcal/mol, D-0(H-OH) = 117.57 +/- 0.09 kcal/mol, and D-0(OH) = 101.79 +/- 0.09 kcal/mol.