The voltammetric behaviour of methylmercury at Nafion® coated glassy carbon electrodes is examined. Cyclic voltammograms recorded at coated electrodes show a dramatic increase of peak currents with respect to bare electrodes, this effect being more evident in perchlorate supporting electrolytes rather than in chloride containing media. Experimental evidence indicates that ion-exchange preconcentration of the cation CH 3 Hg + is the prevailing process, even if the incorporation of neutral species such as CH 3 HgCl by hydrophobic interactions cannot be neglected. The application and optimization of pulsed techniques like differential pulse voltammetry and Osteryoung’s square wave voltammetry, indicates the possibility to use Nafion® coated electrodes for the determination of trace methylmercury at submicromolar levels. The analytical performances can be further improved by using, at the Nafion® coated electrode, a multiple pulse technique named multiple square wave voltammetry. The application and optimization of this technique to the system under investigation is presented and discussed.