Methane gas is an ever-present problem facing the underground coal mining industry. Mine operators are mandated by law to maintain safe concentrations of methane gas within the mine environment. Ventilation is the method of choice used by all mine operators to reduce gas concentrations. When gas emissions are such that ventilation alone cannot control the gas, methane drainage methods must be applied. In the 1970's, there was a concern that unprecedented gas emissions would be experienced as mine operators began new developments in the deep and Gassy Blue Creek and Pocahontas No. 3 Coalbeds. Such concern was well founded as significant gas volumes are being emitted as these mining operations mature. In 1971, the U.S. Bureau of Mines began to tabulate and track the change in mine emissions. These data were extracted from the underground coal mine quarterly air quality-quantity inspections performed by the Mine Safety and Health Administration. At that time, approximately 6,560 mm3/d (231.7 MMCFD) of gas was emitted from 430 underground coal mines. It was determined, however, that the mines emitting less than 2,832 m3/d (100 mcfd) contributed only 2.1 pct of the total daily gas flow. In 1988, underground coal mines emitted 8,350 mm3/d (294.9 MMCFD) from 487 mines. This report evaluates the changing nature of U.S. mine gas emissions over the last 18 years.