Matrix metalloproteinase-8 (MMP-8), also known as collagenase-2 or neutrophil collagenase, was long thought to be expressed solely by maturing neutrophils, and functionally restricted to ECM breakdown. Recent experiments, however, have revealed that this protease can be expressed by a wide variety of cell types and that it plays an important regulatory role in both acute and chronic inflammation. This review intends to give the reader an overview of the most interesting recent findings concerning the role of MMP-8 in inflammation and in cancer progression.