Unbalanced operation of distribution systems deteriorates power quality andincreases investment and operation costs. Feeder reconfiguration and phaseswapping are the two main approaches for load balancing, being the formermore difficult to execute due to the reduced number of sectionalizing switchesavailable in most distribution systems. On the other hand, phase swappingconstitutes a direct, effective and low cost alternative for load balancing. The main contribution of this paper is the proposal of an optimization model anda solution technique for phase balancing planning in distribution systems. Asregards the optimization model, a mixed integer nonlinear programming formulationis proposed. On the other hand, the proposed solution techniqueconsists on a specialized genetic algorithm. To show the effectiveness of theproposed approach, several tests are carried out with two distribution systemsof 37 and 19 buses, this last one with different load models. Results showedthat in addition to the achievement of the primary objective of loss reduction,phase balancing allows obtaining other technical benefits such as improvementof voltage profile and alleviation of congested lines.