A method for the determination of ofloxacin (OFL) has been developed, based on the enhancement of resonance light scattering (RLS) of OFL in the presence of alizarin violet 3B (AV3B). Under the experimental conditions, the RLS intensity of AV3B was greatly enhanced by adding OFL. At pH 5.09, the enhancement of the RLS intensity at 439.5 nm was proportional to the concentration of OFL in the range 0.10-2.50 microg/ml. The detection limit (3sigma) was 0.013 microg/ml. At pH 6.90, the enhancement of the RLS intensity at 405.0 nm was proportional to the concentration of OFL in the range 0.05-3.00 microg/ml. The detection limit (3sigma) was 0.021 microg/ml. The proposed method with high sensitivity, selectivity and reproducibility was satisfactorily applied to the determination of OFL in human serum.