In this review, the proposed mechanisms, catalytic activities and reaction kinetics of catalytic water oxidation with transition metal complexes in homogeneous systems published from 1979 to 2010, with an emphasis on the last decade, are discussed. These metal complexes include mononuclear, dinuclear and multinuclear manganese, ruthenium, iridium, iron and cobalt complexes. Electrodeposited cobalt complexes are a type of heterogeneous water-oxidation catalyst; however, these complexes are discussed herein because they are topological analogs of the Mn cluster in the OEC. MVO species (M = Mn, Ru) as the key active species in homogeneous catalytic evolution of O2 are common feature in many catalysts, in which formation of the OO bond can be achieved either by intramolecular elimination of dioxygen from two MVO groups or by nucleophilic attack of OH鈭?/sup> species on MVO groups. Another common feature appears from tetranuclear ruthenium complex 71, manganese complex 10 and cobalt complex, all of these cubane structural complexes have self-repair properties similar to OEC-protein complex in nature.