The goal of this research has been to acquire experimental data and develop mathematical models in order to analyze results from laboratory-scale and field-scale experiments on underground coal gasification (UCG), especially for low-rank coals such as Texas lignite. Experimental data for water injection in a combustion tube, coal core combustion, and coal block gasification are reported; in parallel, a mathematical model for the combustion tube temperature profile and gas composition was developed which compared favorably with experimental data. A mathematical model for predicting gas composition and coal recovery in the Hoe Creek field experiment has been completed and verified with field data. Two experiments have been constructed to obtain data on reactions of interest to UCG; these include an apparatus for determining the kinetics of tar cracking and a microreactor for analyzing the process dynamics of the water gas shift reaction carried out in a fixed bed catalytic system. 44 refs., 60 figs., 22 tabs.