Example drugs have been examined at platinum and gold rotating disc electrodes in 0.1 mol l^–1 sulphuric acid, and for spiperone over the pH range 0–7. Aceperone and haloperidol show neither anodic nor cathodic activity. Benperidol and droperidol are anodically active, but the voltammograms do not obey the Levich relationship, and adsorption destroys electrode activity. Spiperone gives a two-electron wave for oxidation of the diazo ring; electrode kinetic parameters have been evaluated. Although relative standard deviations of less than 1% are obtainable in the determination of spiperone, adsorption is severe and caution is required.