The family of tissue inhibitors of metalloproteinases (TIMPs) presently numbers four distinct gene products that are specific inhibitors of the matrix metalloproteinases (MMPs). The local balance between MMPs and TIMPs is believed to play a major role in extracellular matrix (ECM) remodeling during development and in diseases such as cancer and arthritis. Unlike the other TIMPs, which are soluble. TIMP-3 is unique in being a component of ECM. Mutations in the human TIMP-3 gene cause a dominantly inherited, adult-onset blindness (Sorsby's fundus dystrophy or SFD). In this article, we summarize what is currently known about TIMP-3, discuss possible mechanisms leading up to SFD, and investigate the effect of TIMP-3 on tumor growth. Breast carcinoma and malignant melanoma cell lines were transfected with TIMP-3 expression plasmids and injected subcutaneously into nude mice. Growth curves of the resulting tumors over a period of 6 to 8 weeks demonstrated that increased expression of TIMP-3 resulted in a statistically significant suppression of tumor growth. Deposition of TIMP-3 in the surrounding ECM by tumor cells may inhibit tumor growth by preventing local expansion of tumor, retarding the release of growth factors sequestered in ECM, or inhibiting angiogenesis. TIMP-3 over-expression had no effect on the growth of the two tumor cell lines in vitro. Because recombinant TIMP-3 inhibits endothelial cell migration and tube formation in response to angiogenic factors, we believe that the effect of TIMP-3 on tumor growth seen in this study may be a consequence of its angiostatic action.