Resonance Raman spectroscopy is applied to a Fe-IV oxo porphyrin with imidazolate as the axial ligand. The v(Fe=O) mode is observed at 792 cm(-1), which is 23 cm(-1) lower than that of the analogous 1-methylimidazole complex and similar to that of horseradish peroxidase compound II (787 cm(-1)) at alkaline pH, for which presence of an anionic histidine was previously postulated. This study thus provides a useful model compound of horseradish peroxidase compound II.