This investigation aimed at determining whether a collagenolytic matrix metalloproteinase (MMP-8) present in the oral fluids might attack demineralized dentin and thereby affect the potential for remineralization. Dentin specimens from freshly extracted third molars were demineralized for 14 days in vitro and then remineralized for 7 days in the presence or absence of activated MMP-8. Following treatment the mineral level of the specimens was assessed from the outer dentinal surface using Electron Probe Micro Analysis (EPMA). The findings suggested that the addition of activated MMP-8 to the remineralizing solution led to reduced remineralization in the surface of the dentin. There appeared to be no effect on the remineralization from any dentin bound MMP activity. It appears that MMP-8 may negatively influence the remineralization of demineralized dentin. Keywords: dentin, matrix metalloproteinase, remineralization