An estimated 49 billion tons, or 29 pct, of the coal reserve base to a depth of 1,000 ft in the eastern United States fall in the 28- to 42-in range. Often left out as a consequence of selective mining, it is a paramarginal source that will become increasingly important. At present (1981), all active thin-seam longwalls are located in the eastern coal province, and a number of operations have been suspended due to the erosion of the market for metallurgical coal. Extensive premining studies, appropriate mine planning, reliable equipment that is designed with ergonomics in mind, adequate roof support, intensive training, and strong face discipline are the ingredients that provide a measure of consistency in production for the last 10 to 16 years, particularly in the Pennsylvania bituminous coalfield where single-drum shearers dominate. Plows, which were found to be very productive in suitable strata in Europe, are used in the Pocahontas field. Low-seam four- and six-legged shields have been introduced recently. The future holds automation at progressive levels. The first step is batch control with the benefits of quickly applied roof support and reduction of workmen exposure to environmental hazards.