Advances in coal production over the last 20 years have led to an increase in coal mine gas emissions. These gas emissions, if not effectively managed, may exceed the diluting capacity of the mine’s ventilation system resulting in gas concentrations in excess of statutory limits and the presence of an unsafe condition within the mine. Where such conditions exist it is typical for production to be slowed or stopped until such time as the rate of gas emission is effectively controlled and managed. This paper discusses the findings of a research project based on an underground mine operating in the Bulli coal seam, located in the southern Sydney Basin of New South Wales, Australia. This mine had encountered a large area with poor drainage characteristics, which initially caused production delays and increased drilling cost, and ultimately led to a review of the mine plan and loss of some 3.0 million tonnes of coal reserves. The project involved detailed analysis of the impact on inseam borehole gas production performance from a broad range of coal properties and operational factors. The variables included in the analysis represent coal properties such as rank, type, structure, seam gas, ash and mineralisation and operational factors such as borehole length, orientation, dip and applied suction. From the analysis a number of coal properties and mine controllable, operational factors are identified that have significant impact on gas production. Recommendations are made to optimise gas drainage productivity in light of the conditions present within the mine.