The state-of-art in process integration will be presented for energy conservation in refining and petrochemical industries. The presentation will not only review well-established ideas, concepts, techniques, and methodologies of process integration in the area of energy savings, but also provide recent developments, extensions and applications in the design and retrofit of heat-integrated refinery and petrochemical systems. The presentation will cover how process integration methods can be applied to achieve high energy efficiency and low emissions by providing the optimal set of operating conditions and/or configurations when increased throughput, changes in feedstocks, and changes in product specifications are to be accommodated.