Tissue inhibitors of metalloproteinases (TIMPs) are specific inhibitors of the multi member family of matrix metalloproteinases (MMPs). Since MMP function is fundamental to events that require tissue remodelling, TIMPs regulate normal biological processes by inhibiting MMPs, and are of importance in pathological conditions. In this chapter we review evidence for the suppressive role of TIMP-1 in the malignant progression of cancer and of its regulatory function in controlling invasion during blastocyst implantation and development.