Ever since its discovery in yeast more than a decade ago [1], Cdc25 has continued to surprise and intrigue researchers. This dual-specificity protein tyrosine phosphatase (dsPTPase) and other members of the protein tyrosine phosphatase family (PTPases) have only recently joined the protease and kinase enzyme families in drug discovery efforts. The role of phosphatases in tumourigenesis was reviewed recently by Parsons [2]. He is arguing that the phosphatase family of enzymes is involved in a variety of cancers and thus poses both a challenge and an opportunity for new therapeutics. The general biology and biochemistry of Cdc25 were recently reviewed [3]. Here I shall first summarize the recent literature on the role of Cdc25 in disease, as well as on new insights into the regulation of this family of proteins. In the second part, I will review current knowledge of the Cdc25 protein structure and the chemical structures and activities of published Cdc25 inhibitors.