The susceptibility of vitronectin (Vn) purified from human plasma to digestion by matrix metalloproteinases (MMPs) was examined. MMP-2, -3, -7 and -9 except for MMP-1 degraded Vn into multiple fragments. MMP-7 showed the highest activity to the substrate among these MMPs, digesting 8-, 30-and 44-fold more preferentially than MMP-2, -3 and -9, respectively. These data suggest that MMP-2, -3, -7 and -9 may be responsible for the pathological degradation and/or normal turnover of Vn.