A wide range of transition metal complexes have been prepared containing the aforementioned ligands with [Au(P4)]+ cations and dinuclear compounds of the type [(PtClMe)2(μ-P2N2)] being of particular current interest as potential antitumour agents. Many of these complexes have shown potent in vitro antiproliferative activity against a range of murine and human tumour cell lines, and in the case of [Au(P4)]+ and their silver(I) analogues, ovarian cisplatin resistant cell lines. All of the gold(I) complexes have been shown to rapidly accumulate in mitochondria by virtue of their lipophilic, cationic nature and in most cases to inhibit the activity of ATP synthase leading to rapid cell death. Furthermore, complexes of the type [Au(P4)]+ have been shown to selectively target mitochondria that have a relatively high mitochondrial membrane potential. These biological studies have been carried out through a collaborative effort with a biochemist, Dr Paul Waring. Current work in this area is geared towards the development of a gold(I)-based antimitochondrial antitumour agent.