Optimal reactive power and voltage control for distribution system involves the installation of fixed shunt capacitors and tap changing voltage regulators along distribution feeders. This can improve voltage profiles for all end-use customers and reduce real power losses. In this book, the fuzzy logic optimization technique is studied and applied to solve the capacitor allocation problem in radial distribution systems. Using voltage regulator for voltage control of radial distribution systems is also studied to allow more loss reduction and to improve the whole system voltage profile. The applicability of the fuzzy logic technique in the field of capacitor placement problem is discussed. Modifications are made to existing fuzzy membership functions to obtain better results. Also, an approach using tap-changing voltage regulators is applied to maintain the voltage profile on a general radial distribution system within a pre-specified bandwidth. In addition, the action of the regulators is studied to provide the best possible profile while maximally decreasing system losses; this is done by controlling the regulator tap positions.