© 2022 Union of Chambers of Engineers and Architects of Turkey. All rights reserved.Underground coal gasification (UCG) is a promising method to utilize deep coal resources that cannot be extracted with conventional techniques and to produce relatively cleaner energy from coal. There have been several laboratory and pilot-scale experiments conducted on UCG within hundred years. Some field-scale trials were conducted for experimental purposes, on the other hand, some others were applied for commercial interests. During these trials, the energy industry has built up experience, developed field demonstration strategies and put forward screening criteria for applicable field selection. In this study, UCG field demonstration strategies, and screening criteria are investigated. Some problems that are encountered with UCG are analyzed, and the engineering precautions are underlined. General information regarding all field trials is summarized, and some important trials are given in detail.