A novel and convenient method of monitoring the internal surface area of a porous silicon layer formed on an n‐type substrate has been developed. The technique has been employed during electrochemical growth and subsequent chemical leaching of porous silicon layers in hydrofluoric acid/ethanol. The method involves periodic interruption of the anodization current to allow insitu measurement of the interfacial capacitance under forward bias using a triangular voltage wave form. The observed evolution of the internal surface area is related to the development of photoluminescence.