Abstract: Due to the continuous change in load, the frequency and tie-line power of control areas get disturbed from their scheduled value which is undesirable. Automatic Generation Control (AGC) is an essential mechanism in electric power systems which balance generated power and demand in each control area in order to maintain the system frequency at nominal value and tie-line power at its scheduled value. This necessitates an accurate and fast acting controller to maintain constant nominal frequency. The limitations of conventional controllers i.e. Integral (I), Proportional Integral (PI) are slow and lack of efficiency in handling system errors. This paper proposes Particle Swarm Optimization (PSO) technique for AGC of two-area interconnected power system. Firstly, the conventional controllers i.e. Integral (I), Proportional Integral (PI) are used for AGC of two-area interconnected power system. Then PSO based controllers are used and various responses due to various controllers have been compared. The responses of the proposed methods are demonstrated by MATLAB simulations.