Silver ions can be entrapped at the dl-dithiothreitol (HSCH(2)(CHOH)(2)CH(2)SH, DTT) self-assembled monolayer films modified gold electrodes. When the potential was made moving, an anodic peak was observed at about 0.23 V (vs. SCE). When the electrode Au/DTT was modified with dodecyl mercaptan further, more Ag (I) can be accumulated and the peak grows. Conditions, such as solution pH and supporting electrolyte, were optimized for Ag (I) determination. Under the selected conditions, i.e. 0.010 M pH 4.3 potassium hydrogen phthalate, preconcentration time of 5 min at open circuit, the anodic peak height is linear to the concentration of Ag (I) in the small range of 0.6-2.4 muM. The influence of some ions on the determination of Ag (I) was examined. The Br(-) ion makes the peak decrease and NCS(-) makes the peak increase. But the determination is not interfered by 1000-fold Pb(2+), Cd(2+), Hg(2+), Fe(3+), Ni(2+), Co(2+), Cu(2+) and Sn(2+) when EDTA was added into the solution. The mechanism involved was discussed.