Abstract: This paper surveys the research and development of Particle Swarm Optimization (PSO) algorithm for choosing the suitable position and size of Distributed Generation (DG) units within a distribution network. Our discussion first covers the algorithm development of PSO and its use in neural networks. After establishing the foundations of PSO, we then explore its use in sizing and sitting of DG units in distribution network. Future development in PSO algorithm such as combining PSO with other optimization techniques for attaining better results is also discussed in this paper.