A method for the determination of trace amounts of beryllium has been developed, based on ion-exchange spectrofluorimetry. Beryllium reacts with morin to give a highly fluorescent complex, which was fixed on a dextran-type anion-exchange resin. The fluorescence of the resin, packed in a 1-mm quartz cell, was measured directly using a solid-surface attachment. The concentration range of the method is 0.10–0.70 µg l–1, the relative standard deviation 1.4% and the detection limit 0.02 µg l–1. The method was applied to the determination of beryllium in natural waters. The aluminium and calcium levels can be determined first in order to reduce their interfering effect. The proposed method is more sensitive and selective than that using morin alone.