The Bureau of Mines and Old Ben Coal Company concluded a cost-sharing contract in 1975, the objective of which was to demonstrate the Herrin No. 6 Coalbed in southern Illinois can be mined safely by longwall methods. Under the agreement, three longwall panels are to be mined at Old Ben No. 24 Mine. A premining investigation laid the groundwork for specifying a roof support system designed to control hazardous ground. Old Ben Coal Company and Bureau engineers selected lemiscate-type roof shields. A rock mechanics program and geological mapping provide early warning capability and criteria for future equipment design. The effect of mining on the surface was monitored by a surface survey to develop subsidence-prediction criteria for the Illinois Coal Basin. The first of the three longwall panels started up in September 1976 and was completed in May 1977. The major adverse condition was the occurrence of limestone concretions, called coal balls, in massive pods. The shields provided adequate roof control even in faulty ground. Operation of the second panel started on August 1, 1977, following panel-to-panel transfer of the equipment. The accident rate was low.