Although the major product of underground gasification of coal is a low-Btu gas, approximately 5% of the total energy produced is in the form of relatively low-boiling coal tars. These liquid organic compounds, which are produced along with water and the product gas, have been characterized for their potential use as a synthetic liquid fuel. The liquids may also be suitable as a petrochemical feedstock and useful in determining the chemical reactions that are occurring underground. The coal tar material, which was sampled regularly during an underground coal-gasification test, showed variations in boiling ranges of from ambient to 600°F and ambient to 950°F with little or no residue as determined by simulated distillation. The coal tars were separated into tar acid, tar base, and neutral oil fractions. Of particular interest was the tar base fraction, which was examined in detail and showed the major constituents to he nitrogen-containing alkyl pyridines. The specific identification of several pyridines and the relative concentrations of these compounds produced under varying gasification conditions are discussed, Virtually all the nitrogen-containing compounds are weak bases as shown by potentiometric titration. The sulfur content of the acidic, basic, and neutral fractions is 0.2-0.3%.