[en] Platinum(III) is no longer an uncommon oxidation state. Numerous binuclear platinum(III) complexes have been prepared and structurally characterized over the past eight years. These include sulfate-bridged dimers of Dsub(4h) symmetry, [Pt₂(S0₄)₄L₂]^2-, L = H₂O, DMSO; phosphate-bridged complexes [Pt₂(HPO₄]₄→(H₂O)₂]^2- and [Pt₂(H₂PO₄)(HPO₄]₃(py)₂]; POP H₂P₂O₅^2--bridged ions [Pt₂→(POP)₄X₂]^2- X = halide; an extensive series of α-pyridonate (C₅H₄NO^-)-bridged head-to-head and head-to-tail complexes, [Pt₂(NH₃)₄(C₅H₄ NO)₂XY]^- X, Y = NO₃, NO₂, H₂O, Cl, Br; n = 2, 3; and organometallic derivatives such as [PT₂(CH₃)₄→(CF₃CO₂)₂(4-Mepy)₂]. In all cases there is a Pt-Pt single bond of length 2.47-2.7A, pseudo-octahedral geometry about platinum, and two or more bridging ligands. The complexes are stable in solution and some undergo quasi-reversible two-electron redox reactions. Mononuclear platinum(III) complexes are less well characterized structurally, but have been stabilized in diamagnetic host lattices in the solid state and by macrobicyclic cage ligands in solution following pulse radiolytic or γ-irridation of precursor platinum(II) complexes. The first unequivocal, crystallographically characterized mononuclear platinum(III) complex, [Pt(C₆Cl₅)₄], has just been reported