The amperometric determination of dopamine under controlled convective conditions on an enzymatically modified carbon paste electrode was studied using potato tissue as a source of polyphenol oxidase. Enzymatic kinetic constants and substrate diffusional-resistance parameters were determined and an analysis of the most common interferents was made. It is concluded that the electrode is suitable for the quantification of dopamine with a detection limit as low as 2.5 x 10(-6) M when the hydrodynamic conditions are carefully controlled. The electrode is active towards dopac, ascorbic acid and pyrocatechol but not L-tyrosine, L-dopa, homovanillic acid, adrenaline, normetanephrine and vanilmandelic acid.