Several thousand tonnes of He-3 have been identified in various terrestrial reservoirs. The He-3 exists, however, as a dilute component, 10−9 to 10−12 volume fraction, of host gase such as the atmosphere or natural gas (methane). The production of He-3 is controlled, therefore, by the usage of the host gases. If the He-3 were separated from the host gases currently used, only 6 kg/yr would be obtained. With a vigorous expansion in the use of natural gas containing significant quantities of He-3, the production of He-3 could be increased to ∼ 25 kg/yr by the year 2000. This quantity of He-3 utilized in the d/He-3 fusion reaction would be sufficient to supply continuously several 100 MW fusion electrical power demonstration plants.