Platinum complexes of the type [Pt(PL)(AL)]2+ where PL is a derivative of 1,10-phenanthroline and AL is cis-1,4-diaminocyclohexane (1,4-dach), have been synthesised and characterised by ultraviolet spectroscopy, elemental microanalysis, nuclear magnetic resonance and X-ray crystallography. The calf-thymus DNA binding affinity of these complexes was determined by isothermal titration calorimetry, revealing higher DNA affinity than their 1S,2S-diaminocyclohexane analogues. In vitro cytotoxicity was assessed in eleven human cell lines, revealing unexpectedly low activity for the 1,4-dach complexes.