A technical analysis is made of both the reverse combustion and forward gasification phases of the Hanna III UCG Field Test. Stability theory and a linear combustion model are combined to determine the characteristics of the reverse combustion linkage channel. Material balance calculations substantiate the accuracy of these predications. These data have important implications concerning the operation of a field test. A forward combusting model is used to calculate the amount and heating value of the gas produced with good accuracy. A necessary input parameter to the model is the rate of water influx. To determine this quantity for earlier field tests, a material balance based on field test results was used. For Hanna III, however, a recently developed water influx model has been used instead. Thus, the combined theories are fully predictive with no field test data used in the calculations. Water injection, which was necessary because of very high well head temperature, greatly complicates the technical analysis.