A simple and selective method to determine norfloxacin using an optical flow-through sensor has been developed. The present sensor was prepared by packing anionic ion exchange resin in a glass tube, followed by introducing KMnO(4) solution to the glass tube for immobilization on resin. The optical sensor is based on the emission intensity from the Tb(III) solution sensitized by norfloxacin. The excitation of norfloxacin occurred by the chemiluminescence from the reaction of KMnO(4) and Na(2)SO(4) solutions. The effects of pH, concentration of Tb(III) ion, KMnO(4) and Na(2)SO(4) solutions and flow rate of the norfloxacin solution on the chemiluminescence intensity were studied to find the optimum experimental conditions. The emission intensity increased linearly with increasing norfloxacin concentration from 1.0 x 10(-3) to 1.0 x 10(-8) M and the detection limit (3sigma) was 8.7 x 10(-9). The applicability of the present method was demonstrated by determination of norfloxacin in various pharmaceutical preparations and serum sample.