This lecture briefly explain technical evolution of 3G System. The third generation (3G) cellular networks were developed with the plan of present high speed data and multimedia connectivity to subscribers. The International Telecommunication Union (ITU) provides the standard known as, IMT-2000 (International Mobile Tele commmunications-2000 for 3G system. Here brielt explain on UMTS System Architecture, UMTS Network Architecture and CDMA2000 evolution to 3G.