A novel method for the determination of perphenazine has been developed. The method is based on the accumulation of perphenazine at a gold electrode modified with decanethiol (DEC) self-assembled monolayer (SAM) and its oxidation at about 0.6 V (vs. saturated calomel electrode (SCE)). Because some coexistent electroactives were blocked and perphenazine was selectively accumulated by the SAM, the electrode exhibited good selectivity and sensitivity. Various conditions were optimized for practical application. Under the selected conditions (i.e. 0.05 M pH 10 sodium borate buffer, accumulation time: 120 s, accumulation potential: -0.4 V, scan rate: 100 mV s(-1)), the anodic stripping peak current was linear to perphenazine concentration in the ranges of 6x10(-9)-5xl0(-7) and 5x10(-7)-5x10(-6) M with correlation coefficients of 0.998 and 0.995, respectively. For a 1.0x10(-6) M perphenazine solution, the relative standard deviation of peak height was 2.3% (n=8). This method was applied to the determination of perphenazine in some drugs and the recovery was 92-101%. In addition, it was found that in the presence of perphenazine, the SAM structure changed a little and more needle holes appeared. However, the SAM could recover the original form when perphenazine and its redox product were removed from the monolayer by repeatedly cycling the electrode in a blank solution for a minute. The modified electrode was characterized by alternating current impedance and electrochemical probe.