In this paper, we proposed a methodology for optimal sizing and placement of a distributed generation in IEEE 33 bus and IEEE 69 bus radial distribution networks using Parameter Improved Particle Swarm Optimization technique (PIPSO). Since the distribution line loss minimization plays a vital role in economic operation of power system, the distribution line active power loss has been elite as the fitness function for each particle in the proposed algorithm. The computer simulation has been carried out in MATLAB software and the results incurred from the proposed approach evidences that better real power loss reduction and improved bus voltage profile when compared with other existing algorithms. © 2015 IEEE.