This report presents the results of tests conducted on 554 specimens of carbon and carbon-molybdenum steel removed from petroleum refining equipment and examined for evidences of graphitization.Graphite formations were found in 33.8 per cent of these specimens.It has been established that some steels have a greater tendency to graphitize than others; and that high aluminum content (in excess of 0.015 per cent), high operating temperatures, and the steel-making process used in meeting certain specifications are factors which affect graphitization.Of the steels examined, ASTM A I06 pipe indicated the highest tendency to graphitize; and, of the carbon steels, ASTMA 285 plate material indicated the highest resistance to graphitization. Connected nodules of graphite were found in both carbon and carbon-molybdenum steels.Although the carbon-molybdenum steel graphitized less frequently than the carbon steel, when it did graphitize, graphitization was of the more serious type.