Inhibitors of matrix metalloproteinases (MMPs), enzymes involved in the processes of tumor growth, angiogenesis, invasion and metastasis, represent a promising new potential approach to cancer therapy. Several synthetic inhibitors of MMPs have been developed, many of which are currently in clinical trials. This review will describe some inhibitors of MMPs, presenting results of preclinical studies and, where available, their current clinical status as well. Issues concerning the use of MMP inhibitors, the design of clinical trials and the assessment of clinical response will also be addressed.