The main purpose of this paper is to review existing knowledge on metal alloy behaviour in contact with highly reducing syngas in coal gasification plants, presently close to commercialization. A secondary purpose is to compare laboratory and plant corrosion data. Present commercial practice indicates that most metal alloys will be used as heat exchangers to evaporate steam at 350–450°C. Smaller but significant future applications may be superheaters or hot-gas clean-up equipment exposed at 500–600°C. The alloys will probably be in contact with non-equilibrium gases quenched from much higher gasification temperatures in the range 1000–1500°C. Under these conditions the formation of chromia- rich protective oxide scales is rarely observed. The growth rate of less protective oxide/sulfide scales varies considerably with temperature, gas composition and alloy composition. For most applications, available Fe-Cr-Ni alloys can be found to provide adequate service life, provided carburization after long exposures can be avoided.