Capacitances, C, in KCl solution and Faradaic currents, I, of a ferrocene derivative were obtained at the polycrystalline gold electrode coated with self-assembled hexadecanethiol monolayer when temperature, T, was continuously varied. Both capacitances and currents increased with temperature (from 0 to 70 degreesC). Curves of DeltaC/DeltaT vs. T were composed of two different lines, exhibiting large variations at T-c (ca. 45 degreesC). A similar variation was also found at curves of DeltaI/DeltaT vs. T for the oxidation current, I, of ferrocene derivative. The critical variation suggests phase transition of the SAM.