The recent interest in inhibitors of farnesyl:protein transferase (FPTase) has resulted in a better understanding of the enzymology of this protein. Rationally designed inhibitors of prenyl transfer have emerged as potential new drug candidates because of the insight gained over how a prenyl group is enzymatically transferred onto a peptide thiol. This paper will explore how advances in our understanding of FPTase mediated catalysis has affected the design of FPTase inhibitors as possible cancer therapeutic agents. Without structural information of the enzyme, substrate analogues comprise the first area of drug design: these include peptidomimetics of the four C-terminal amino acids of rasP21 as well as farnesyl diphosphate analogs. In addition, phosphate anion was found to enhance the inhibitory potency of certain compounds known to be competitive with respect to farnesyl diphosphate and therefore incorporation of the phosphate anion may also provide a basis for improved inhibitor design.