The temperature of synthesis gas (syngas) leaving a gasifier could be as high as 1600°C, depending on the gasification process employed. Recovery of heat from the high temperature syngas is essential for attaining high process efficiency. Heat recovery systems can reclaim a significant portion (5–25%) of the energy in the feed, depending upon the technology used. It is estimated that compared to a gasification plant without hot syngas heat recovery, the use of a heat recovery system can increase the process efficiency by approximately 5 percentage points. High temperature syngas can be cooled using a radiant, a convective, a direct quench cooler or any combination of these coolers. The selection and actual design of a syngas cooling system are influenced by factors such as the type of gasifier used, the characteristics of the coal feed, the overall gasification process application and costs. Various high temperature syngas cooling systems based on mature technologies have been developed to meet varying technological challenges and process requirements. This report reviews all types of commercial high temperature syngas cooling and heat recovery systems. The design concepts and operating experience of the syngas cooling systems in commercial scale IGCC plants are examined and discussed.