The influence of active filler materials, in this study carbon black, on the sulfur vulcanization process is examined by using sulfur K-edge X-ray Absorption Near Edge Structure (XANES) measurements. As a well defined reference system, silane coupling agents Si69 and Si266 (Degussa-Huls trade names) containing polysulfidic or disulfidic crosslinks, respectively, were investigated in pure state and mixed with carbon black. Comparison with reference spectra and a quantification of sulfur crosslink distributions led to the result that carbon black aids in the formation of long sulfur chain crosslinks. To transfer these findings to the process of vulcanization, they have been verified by investigating XANES spectra of two compounds, containing no accelerator, without filler or with a contribution of ten phr carbon black. The results give evidence of carbon black leading to an accelerated cracking of the elemental sulfur rings, which then form the intermolecular crosslinks. This effect may explain the reduced scorch times seen in the rheometer curves of filled rubber compounds.