Carbon diffuses into metal and recrystallizes as graphite, which is termed graphitization of carbon by metal. This study has revealed that the temperature at which this graphitization occurs depends on the initial state of the carbon. The lowest temperatures at which graphitization by Ni occurs for diamond, diamondlike amorphous carbon, graphite, and graphitelike amorphous carbon were 700, 500, 900, and 700 °C, respectively. It is shown that the temperature ranges at which graphitization by Ni occurs are correlated to the temperature ranges at which graphite can be formed on Ni by chemical vapor deposition using organic substances as starting materials. ©1997 American Institute of Physics.