Cathodic protection (CP) system objective is to protect metallic structures against corrosion caused by chemical reaction between metallic structures and surrounding medium such as soil or water. To overcome such a problem a sacrificing anode is connected to the protected structure (which acts as a cathode) through a d.c. power supply. The d.c. power required for CP systems is characterized by low voltage and high current. This power may be obtained from a.c. power source, if available, and a rectifier. The second alternative is to use a diesel generator and a rectifier, but this system requires frequent fuel addition and maintenance. If the location of the system is remote, maintenance and fuel transport become costly. Recently solar photovoltaic (PV) systems are used to provide cathodic protection systems in remote areas by d.c. power. Solar PV systems are modular sc that they may be designed to operate at the required voltage and current easily. PV systems are maintenance free. To stop the corrosion entirely, the protected structure is to be fed by a constant current determined by structure＇s metal area and the surrounding medium. The major difficulty to achieve this goal is the variations of the surrounding medium resistivity due to climatic conditions changes. Conventional CP systems resolve this problem by periodical manual adjustment of the d.c. voltage to obtain a constant current, Such adjustment depends on the experience of the technician and the accuracy of the measuring equipment used. Moreover if the interval between two successive adjustments is relatively long, an appreciable corrosion may take place because of the non accurate d.c. voltage applied to the system. To overcome this difficulty, an automatically regulated CP system is discussed by Anis and Alfons [Solar Energy, 53(2), pp. 211-214, 1994]. The proposed system senses the variations of surrounding medium resistivity and adjusts the d.c. voltage of the system automatically so that the d.c. current is kept almost constant at the required level regardless of soil resistivity variations. In this work the design of the electronic control circuits of the regulated CP system is thoroughly investigated.