Serine proteinases fulfill and facilitate a broad spectrum of biological processes. They are held in check by different specific inhibitors. This delicate balance can be disturbed by genetic defects or exogenous influences and has been shown as the underlying or promoting cause for a large number of different diseases. For instance, proteinases are under investigation as drug targets for cancer, infections, neurodegenerative diseases, osteoporosis, inflammatory disorders and many more. Dermatological research has contributed greatly to the appreciation of the complex regulatory network between serine proteinases and serine proteinase inhibitors. In addition, proteolytically trimmed proteinase-activated receptors (PARs) trigger keratinocyte proliferation and differentiation as well as leukocyte attraction and activation. New insights have been gained particularly concerning the progression of inflammatory disorders of the skin. This review summarizes the role of serine proteinase inhibitors in physiology and pathophysiology of the skin.