The high enthalpy shock tunnel in GWingen (HEG) will he described. The tunnel in GWingen is currently being established for work in tlie hypervelocity flow regime where dissociative effects of nitrogen are significant. This is a free piston driven shock tunnel operating in the reflected mode. In this paper. afler a brief description of llie facility and its operating requirements. the first commissioning results will be described. These show that conditions similar to atmospheric reentry conditions of a space flight vehicle. with specific stagnatioii enthalpies h= 20. corresponding lo flight velocity v= 6.3 (or flight Mach number 21). have been achieved with tcst gas nitrogen.