New oscillating reactions with the participation of a tetraazamacrocyclic nickel (II) complex [NiL](ClO4)(2) as catalyst in the lactic acid/acidic bromate system are reported. The ligand L in the complex is 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene. The oscillating features are described, and the activation energy is found to be as low as 27.2 kJ/mol. Experimental results suggest that the brominating reaction may take place on pyruvic acid, the oxidized product of lactic acid. A tentative mechanism based on FKN is proposed.