A survey has been made of forward combustion gasification models that are available in the public domain. The six models obtained for study have been mathematically analyzed to determine their conceptual completeness and computational complexity. The models range in scope of generality from a simple constrained mass balance model to a two-dimensional unsteady-state model. The computer code for each model has been implemented on the University of Wyoming CDC CYBER 730/760 computer system. Computed analyses with each of the programs are compared using data (taken primarily from the Lawrence Livermore National Laboratory (LLNL) Underground Coal Gasification (UCG) Data Base) corresponding to six representative DOE sponsored field experiments at Hanna, Hoe Creek, Rawlins, and Pricetown. Four of the field tests were air injection experiments and two were oxygen/steam injection experiments. This study provides a direct comparison of input data requirements and computer resource requirements of the six computer codes. It furnishes an indication of the applicability of each model to the various operating conditions in the different field tests. Computational capabilities and limitations of each model are discussed in detail. 20 references, 47 figures, 13 tables.