A novel cathodic electrochemiluminescence (ECL) behavior of the norfloxacin (NFLX)/peroxydisulfate (S2O82-) system in purely aqueous solution at a glassy carbon electrode (GCE) was firstly reported in this paper. The NFLX/S2O82- system could produce a very strong ECL signal under the potential scan from 0 to -1.8 V in 0.1 M phosphate buffer solution (pH 7.0) containing 0.24 mg/mL NFLX and 10 mM S2O82-, which was about 350 times higher than that of S2O82- alone, while NFLX did not produce ECL in the absence of S2O82-. The effects of pH value, S2O82- and NFLX concentration on the ECL intensity were investigated and the possible mechanism for the ECL behavior of NFLX/S2O82- system was proposed. (C) 2008 Elsevier Ltd. All rights reserved.