The electrochemical stability of desmopressin acetate (DDAVP) was investigated. After a direct current of 1 mA was passed through two electrodes chosen from platinum, silver and silver chloride, the decomposition of DDAVP was observed. The degradation products of DDAVP yielded with a Pt(anode) and AgCl(cathode) pair were similar to those observed in an anodic donor after in vivo iontophoresis. Although the Ag(anode)/Pt(cathode) degradation pattern of DDAVP was similar to that of an in vivo cathodic donor HPLC chromatogram, it was different from that of the anodic donor. In the anodic system, the stability of DDAVP was independent of the pH, and decreased with increasing concentration of NaCl.