Résumé : OPA is often used as an off-line derivatisation agent for fluorimetric detection in gentamicin analysis. As, in general, electrochemical detection is more sensitive than fluorimetric detection, the analysis of gentamicin as its OPA derivatives by high-performance liquid chromatography and electrochemical detection is proposed. The derivatisation procedure is that described by the European pharmacopoeia. The method allows not only the detection of all major gentamicin congeners C1, C1A, C2A and C2, but also of other minor unidentified components. A full validation of the method is presented and comparison is made with fluorimetric detection. A good linearity is found for the four congeners within the dynamic ranges 1-50 μg ml -1 for electrochemical detection and 4-80 μg ml-1 for fluorimetric detection. Both methods presented good accuracy and fidelity, although electrochemical detection is more sensitive than fluorimetric detection. The electrochemical detection method presented in this work appears to be a good alternative to the fluorimetric and pulsed electrochemical detection methods. © 2004 Published by Elsevier SAS on behalf of Académie des Sciences.