In October 1979, US Department of Energy successfully completed an underground coal gasification (UCG) field test in eastern bituminous coal near Pricetown, WV. The field test consisted of three major phases: (1) reverse combustion linkage, (2) link enhancement, and (3) gasification. During the gasification phase, gas with an average heating value of 121 BTU/scf was produced, which resulted in an average energy production of 346 BTU/day. Environmental surveys were performed to study the effect of the test on air and water quality. Water was monitored periodically at and near the site in streams, shallow wells, and deep wells before, during, and after the test. Ambient air was monitored continuously over the same period. Between September 12 and October 9, 1979, chemical changes occurred in the groundwater during high-pressure air injection as a result of a casing rupture in a production/injection well 205 feet below ground level. The water monitoring program effectively detected the contamination excursion and followed the deep migration of pollutants. A mass balance model was developed and used for analyzing the test data. Two-dimensional and three-dimensional thermodynamic models were developed to determine the cavity growth during UCG. The cavity growth at the end of gasification was predicted using the 3-D models and was confirmed by the field test data. Two major problems were encountered in the Pricetown I test. The first was related to restricted flow through the linked paths due to the production and buildup of tars and oils in situ. This problem was eliminated by reversing the flow of air alternately until the substances were burned away and the normal passage was restored. The other was related to aquifer pressurization due to rupture casing in one well. This type of problem could be avoided by using proper well completion design.