A mathematical model is presented to study the combustion and gasification of char with air and steam under pressure. A series of curves was obtained from the solutions of energy and mass balances for the probable range of operation in the gasification of char. Certain theoretical conclusions are drawn with respect to gasification of char in a fixed bed and found to be in accord with the results of the literature. A mathematical correlation is presented for conveniently calculating the product gas composition, the burning rate, the combustion zone thickness, the solids＇ maximum temperature, and the outlet gas temperature. This correlation is of general applicability, covers a wide range of operating conditions through use of multiple variance analysis, and may be used for pressures as high as 4200 kPa. Examples are given to illustrate the use and versatility of the correlation.