Coalbed gas compositional data from the San Juan, Piceance, Black Warrior, Powder River, Raton, Cherokee, Greater Green River, and Northern Appalachian Coal Basins were evaluated to determine the compositional variability of coalbed gases among and within basins. Coalbed gas composition varies among coal basins, laterally between wells, and vertically among coal beds within individual wells. Based on gas analyses from nearly 1,400 coalbed methane wells, an average coalbed gas is composed of approximately 93 percent methane, 3 percent carbon dioxide, 3 percent wet gases, and 1 percent nitrogen with a heating value of approximately 1,000 Btu/ft3. Gas dryness indices (C1/C1-5) range from 0.77 to 1.00, and ethane content can exceed 11 percent. Carbon dioxide and nitrogen range from 0 to more than 40 and 11 percent, respectively. Although the compositional ranges for desorbed and produced gases are similar, desorbed coalbed gases may contain more carbon dioxide, ethane, and nitrogen due to the desorption characteristics of these components.