The impedance of rabbit skin has been measured in the frequency range 1–60 kHz using a simple a.c. bridge method and stainless steel electrodes. The effect of four important drugs, namely, adrenaline, noradrenaline, atropine and histamine, has been examined. It was found that all these drugs produced a decrease in the skin impedance in varying degrees, suggesting a penetration of the ions through the underlying layers of the skin. For the purpose of analysis, all these data are compared with their own controls. The order of applying the two drugs adrenaline and noradrenaline at the same site on the skin of an animal does not produce a change in the nature of the relative impedance variation. It was observed that the effect produced by noradrenaline is more pronounced than that by adrenaline. The effect produced by these drugs was compared with that produced by pure hydration of the skin. It was found that the change produced in the latter case is much less than that produced by drugs, thus showing a clear difference between the two effects.