Microbial communities associated with biogenic coalbed methane (CBM) have been investigated extensively by sampling produced water and coal samples. However, little is known about the microbial communities associated with CBM gas. In this study, we employed pyrosequencing and real-time polymerase chain reaction to investigate the microbial communities in CBM gas from a CBM field associated with Ordos Basin in China, where biogenic CBM had been identified and methanogens and related bacteria had been found to be present in coal and produced water samples. The pyrosequencing results revealed that the GOM_Arc_I group, with 993% archaeal sequence reads, was the predominant archaea in gas samples. The main bacteria present in gas samples were Proteobacteria. In particular, the genus Herbaspirillum comprised approximately 76% of bacterial sequences. Most of the detected bacteria had the potential to degrade aromatic and cellulose-derived compounds in coal and promote nitrogen cycling in coalbeds. The microbial diversity in gas was lower than that in coal and produced water, and significant differences were observed in the microbial communities in gas. These results provided insights into the archaeal and bacterial communities associated with CBM gas at this location and may improve our understanding of the current status of archaeal and bacterial communities in CBM fields. (C) 2015 Elsevier B.V. All rights reserved.