Ab initio MO calculations at MP2/6-31G* level were performed on hydroxyl derivatives of tetrazole and their anions. Their fully optimized geometries, electronic structures, IR spectra and thermodynamic functions are reported. The calculation results show that all the titled compounds are practically planar and aromatic. The N4 atom on the ring is most negatively charged. The N-hydroxytetrazoles are more stable than the C-hydroxytetrazoles. The thermodynamic properties of the titled compounds are similar.