We demonstrate the first application of L-edge X-ray absorption spectroscopy (XAS) to the electronic characterization of biological photolysis products. The experimental L-edge XAS spectra of deoxymyoglobin (deoxy Mb), oxymyoglobin (MbO(2)), carbonmonoxymyoglobin (MbCO), and the low-temperature photoproducts (Mb*CO and Mb*O-2) are presented and compared to simulated spectra using a ligand field multiplet calculation. This analysis indicates that MbCO and MbO(2) are both low spin and does not support some previous studies which suggest that MbO(2) has an intermediate spin. Both photoproducts, Mb*CO and Mb*O-2, are different from deoxy Mb in the Fe-II electronic structure. In addition, different low-temperature photolysis intermediates are suggested for MbCO and MbO(2). The L-edge XAS spectra for Fe-III in aquometmyoglobin (met Mb) and azidomet myoglobin (MbN(3)) provide a comparison of the ferrous versus ferric myoglobin species. Finally, the special advantages of using soft X-ray absorption spectroscopy for understanding the electronic transitions coupled to photolysis-induced structural changes are discussed.