Porous silicon (PS), which is composed of silicon crystals with typical sizes in the range of a few nanometers, shows high specific surface. Thus, its particular surface morphology makes this material very suitable for its use in the field of sensing. Accordingly, PS-based devices with the structure metal/PS/silicon/metal were developed to be used as electrical biosensors. Current–voltage measurements have shown that these devices typically show rectifying characteristics. In addition, it has been found that the current–voltage characteristics show a strong variation as a function of the presence/absence and concentration of biomolecules onto the surface of PS, both for longitudinal and transversal conduction. The present work describes our findings in the correlation between biomolecule surface concentration and current for a given voltage.