The synergistic combination of hydrogen peroxide and hypochlorite ion in water results in formation of the highly oxidizing intermediate species singlet oxygen (1O2), which is effective in the oxidation of free cyanide (CN-) in water. The process was fast and efficient over the studied pH range of 9-11, and up to an initial CN- concentration of 1000 mg/L. For an initial [CN-] equal 100 mg/L, pH equal 9, and molar ratio ([H2O2]more[NaClO])/[CN-] equal 1:1 it was possible to achieve a final concentration of [CN-] lower than 0.2 mg/L (99.8 per cent reduction) in t equal 20 min at 25 degrees celsius in a batch reaction. By comparison, the same reaction with either of the separate oxidants (H2O2 or NaClO) at the same molar ratio of oxidant/CN- equal 1:1 resulted in a maximum of 87 per cent breakdown of the cyanide (using NaClO) for the same 20 min reaction period.