The UCG (underground coal gasification) trial was carried out at the Experimental Mine "Barbara" within the RFCS Project HUGE (2007-2010). The georeactor was placed in the coal seam 310 at the depth of 30 m. During the period of 15 days about 22 tons of hard coal was gasified with the average consumption rate of 62 kg/h. The total volume of 71,764 N m(3) of dry gas was produced. The gasified media applied were oxygen, air and water. The average heating value of product gas and thermal power generated in a flare were 3.8 MJ/N m(3) and 211 kW, respectively. The average H-2 and CO contents in product gas were 14.2 vol.% and 13.4 vol.%, respectively. The calculated gasification efficiency was about 56%. The experiment revealed that gasification in thin, shallow-buried coal seams can cause some operational problems, since under such geological conditions high risk of gas leakages exists. The gas leakages strongly affect not only the overall process efficiency but can also cause toxic hazards near the UCG test site. The postburn area venting was necessary for the period of 40 days after the installation shutdown. After this time, the reactor reached its initial thermal conditions. (C) 2012 Elsevier Ltd. All rights reserved.