Cobalt, a refractory metal, is strategically important because its use is essential to the production of many defense-related items. Its largest end use is as a major element in superalloys used in jet engines. The United States, the world's largest consumer of cobalt, produces no cobalt itself and has no reserves. More than 90% of the cobalt consumed in the United States is imported and about one-half of these imports originate in Zaire and other countries in central Africa. Zaire is the world's largest producer of cobalt and has, by far, the world's largest reserves of cobalt. This creates a strategic problem for the United States in that cobalt supply from central Africa is subject to disruption. This Bureau of Mines report presents comprehensive data on cobalt including strategic considerations, problems, technology trends, reserves-resources, supply-demand relationships, economic factors and problems, operating factors and problems, and outlook to 2000.