The active site of the NiFe-hydrogenase from Desulfovibrio vulgaris Miyazaki F was investigated by means of X-ray Absorption Spectroscopy (XAS). Using the Extended X-ray Absorption Fine Structure (EXAFS) the active site was structurally characterized to determine differences between four different catalytic states of the enzyme. The nature of an additional ligand which is present in the oxidized forms of the enzyme was revealed and the distance between both metal atoms of the heterobinuclear site was calculated. Suitable data analyzation techniques were developed using simulated spectra. For the verification of these techniques, spectra from model compounds structurally characterized by other methods were used. To ensure sufficient quality of the spectra a newly developed quality control system using statistical criteria was employed.