This paper presents a simple, rapid, and accurate method suitable for on-site measurement of short-chain volatile fatty acids (SCFA) in various environmental samples. This fluorimetric method involves a derivatization step of SCFA with N-(1-naphthyl)ethylenediamine (EDAN) and allows determination of acetic, butyric, propionic, valeric, lactic, succinic, and p-hydroxybenzoic acids in approximatively 10 min. To evaluate specificity and accuracy of the method, both laboratory-made waters and real samples ranging from wastewater plant and river to soils and composts have been tested. Good accuracy and correlation (r(2) = 0.9887) with HPIC determination have been obtained. The potential interference effect has been taken into account with compounds like humic substances, alcohols, amines, aldehydes, and metallic ions. This method seems thus well designed for the determination of total SCFA in waters, in the range 0.84-500 mg/L. Because this method seems well suited for following of anaerobic treatment, it has been calibrated versus acetic acid-equivalent.