About 90% of the world's bioenergy is produced by burning renewable biomass fuels. While the overall thermodynamic efficiency of a power boiler’s steam cycle can be increased by raising its maximum steam temperature higher superheater tube temperatures also promote pluggage and accelerated corrosion. Low-cost biomass fuels such as agricultural wastes typically contain more alkali metals and chlorine and less sulfur than the black liquor burned in recovery boilers. Therefore adding biomass to a boiler’s fuel typically lowers the temperature at which ash deposits melt on superheater tubes. The chromia-forming boiler tube alloys that are commonly used to resist high temperature oxidation can suffer fluxing by forming alkali chromates and volatilization by chromic acid formation. This paper will review recent research on superheater corrosion mechanisms and superheater alloy performance in boilers burning black liquor and in boilers burning blends of biofuels with fossil fuels or municipal wastes.