In the fall of 1972, the U.S. Bureau of Mines began an experiment to investigate the technologic, economic, and environmental considerations of underground gasification of a W. subbituminous coal. The gasification site is near the town of Hanna, Wyo., approx. 70 miles northwest of Laramie. The test results indicate that gas volumes and gas heating values have fluctuated over a wide range depending on operating conditions. The ranges have been from 50,000 to over 3 MMscfd of produced gas with a composite heating value from 30 to 465 btu per scf. Even though these fluctuations have occurred, a semisteady state condition existed for a 6-mo. period. From Sept. 1973 through Feb. 1974, a low btu gas averaging about 130 btu per scf was produced at an average rate of 1.6 MMscfd. A material balance made during this period indicated: (1) there was little or no underground gas leakage from the site; (2) about 80 bbl of formation water were consumed each day; (3) between 13 and 46 tons of dry coal were affected each day depending on the assumptions made; and (4) from 23 to 65% of the energy of the coal being subjected to carbonization and/or gasification is being recovered.