In this article, the results from a pilot-scale, underground coal gasification (UCG) experiment conducted in an operating coal mine "Wieczorek" were presented. The 60-day gasification trial demonstrated that through the appropriate selection of the test site and by applying all safety standards essential for the coal mining industry, UCG in an active mine can be conducted safely and efficiently. The idea of the technical realization of the UCG process, as well as selected gasification results, such as the primary mass balance parameters, gas production rate, coal consumption rate, coal gasification efficiency and the changes in gas composition, were presented. (C) 2016 Elsevier Ltd. All rights reserved.