Hanna II yielded several outstanding accomplishments in the field of UCG using air injection. These were the following: production of the highest gross heating value product gas over the longest duration ever reported; operation at the highest thermal efficiencies ever reported; highest production rate from any UCG test in the Free World; high overall sweep efficiency for parallel two-well patterns; and the most thoroughly instrumented UCG test ever conducted. Based on the results of Hanna II, a large number of predicted problem areas attributed to in-situ coal gasification technology do not appear to be of significance. Stable operation at high production rates with relatively constant gas quality and composition have been achieved. Overall process and thermal efficiencies were high and resource recovery was excellent. No detectable gas leakage occurred based on nitrogen and argon balances. No shutdown due to equipment or process failure was encountered. Process control based on adjustment of air injection rate to maintain the optimum air/water ratio appears feasible. Further tests planned at Hanna will concentrate on further demonstration of these conclusions and will address the major unknowns still associated with the in-situ coal gasification process, i.e., the effects of subsidence and the determination of optimum and maximum well spacings.