Abstract A program was initiated to determine the extent of the coalbed methane resource and the location of the most favorable resource areas within the Illinois basin, and to obtain a better understanding of the relationships between selected variables and the gas content of coals. Preliminary gas in-place resource estimates are made based on coal desorption data and the most favorable resource areas are outlined. Limited and/or poor data precluded establishing relationships between various geological-chemical/physical parameters and coal gas content. Further investigations are required to determine such relationships and to define what percentage of this resource is producible.