A differential-pulse polarographic method for the determination of Se is described. The effect of Cu, Pb and Cd on the Se peaks was studied. In order to find a suitable medium, HClO4 (pH 1), 0.1 mol dm-3 KNO3 (pH 4), a buffer solution of pH 4(CH3COOH-H3BO3-H3PO4), a buffer solution of pH 9 (NH3-NH4Cl) and 10% Na2SO3 (pH 9.5) were studied. In NH3-NH4Cl and 10% Na2SO3 media the expected peak for SeO3(2-) was not observed; however, the SeSO3(2-) ion gave a peak at -800 and -600 mV, respectively. In addition, in the CH3COOH-H3BO3-H3PO4 buffer solution of pH 4, SeO3(2-) gave two peaks at -610 and -1310 mV. The detection limit for Se in a buffer solution (pH = 4) of CH3COOH-H3BO3-H3PO4 was 1 x 10(-8) mol dm-3. The method was applied to some environmental samples.