An aqueous solution composed of [Zr(H2O)2edta]·2H2O and 3-hydroxyflavone (flavonol) exhibits an intense blue fluorescence (Λmax = 460 nm) upon excitation at 400 nm and the signal intensity decreases with the addition of fluoride ion. This observation has been interpreted by the ligand exchange of flavonol coordinated to Zr(iv) with fluoride ion. Based on this phenomenon, we have fabricated a simple fluorescent detection system of fluoride ion available in aqueous media. The present signaling system provides a simple, rapid and selective detection method of fluoride ion, which covers the concentration range from 1 × 10−3 to 3 × 10−6 M without any significant interference from common anions. © 2002 The Royal Society of Chemistry.