The helium resources base of the United States was estimated by the Bureau of Mines to be 1,040 bcf as of January 1, 1987. These resources are divided into four categories in decreasing degree of assurance of their existence: (1) helium in storage and in proved natural gas reserves, 265 bcf, (2) helium in probable natural gas resources, 228 bcf, (3) helium in possible natural gas resources, 320 bcf, and (4) helium in speculative natural gas resources, 227 bcf. These helium resources are further divided into depleting and nondepleting, with the helium in storage being in a separate classification. The depleting resources are those associated with natural gasfields that are, or will be, produced for the natural gas they contain. Almost all of the helium in potential (probable, possible, and speculative) natural gas resources is included in this classification. These depleting resources are estimated to contain 951 bcf of the total helium resource base. Helium resources contained in nondepleting natural gas resources, i.e., those in shut- in, abandoned, or otherwise nonproducing natural gasfields, are estimated to total 53 bcf. There is 36 bcf of helium in storage in the federal government-owned Cliffside gasfield near Amarillo, Texas.