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 predictions. These data have important implications concerning operation of a field test. A forward combustion 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 in time model has been used instead. Thus, the combined theories are fully predictive with no field test data used in the calculations. Water injections, which was necessary because of very high well head temperatures, greatly complicates the technical analysis.