A new fluorescent reagent 2,4-dihydroxyacetophenone benzoylhydrazone (DHAPBH) was synthesized and its ionization constants were established spectrophotometrically. The fluorescent reaction of this reagent with cadmium was studied. The cadmium ion can form a stable binary chelate with DHAPBH, having a mole ratio of 1:2 in the pH range of 3.6-4.4. Based on this chelation reaction, a highly sensitive spectrofluorimetric method was developed for determination of trace amounts of cadmium in a water-ethanol (7:3 in volume ratio) medium at pH = 4.0. Under these conditions, the Cd-DHAPBH complex has excitation and emission maxima at 306 and 437 nm, respectively. The linear range of the method is from 0.36 to 140 μg?L?1 and the detection limit is 0.27 μg?L?1 of cadmium. Interferences of other ions were stud- ied. The method was successfully applied to the determination of cadmium in mineral water, tap water, river water, and wastewater. A new fluorescent reagent 2,4-dihydroxyacetophenone benzoylhydrazone (DHAPBH) was synthesized and its ionization constants were established spectrophotometrically. The fluorescent reaction of this reagent with cadmium was studied. The cadmium ion can form a stable binary chelate with DHAPBH, having a mole ratio of 1: 2 in the pH range of 3.6-4.4. Based on this chelation reaction, a highly sensitive spectrofluorimetric method was developed for determination of trace amounts of cadmium in a water-ethanol (7: 3 in volume ratio) medium at pH = 4.0. Under these conditions, the Cd-DHAPBH complex has excitation and emission maxima at 306 and 437 nm, respectively. The linear range of the method is from 0.36 to 140 μg · L -1 and the detection limit is 0.27 μg · L -1. 1 of cadmium. Interferences of other ions were stud- ied. The method was successfully applied to the determination of cadmium in mineral water, tap water, river water, and wastewater.