The role of chloride in the corrosion of oil- and coal-fired boilers and gas turbines, by flue gases and their deposits, is discussed, on the basis of both experimental and theoretical studies. It is concluded that in most boilers, the presence of chloride in the fuel will not result in any serious increase in the rate of corrosion of plant components. On the other hand, a number of situations are identified, which can arise in both boilers and gas turbines, in which high chloride levels in the fuel can be associated with enhanced rates of corrosion.