Two methanogenic strains, 8-2T and 4-1, with rod-shaped (0.4-0.5 x 3-5 microm), non-motile cells, sometimes observed in chains, were isolated from two anaerobic digesters in Beijing, China. The two strains used H2/CO2 and formate for growth and produced methane. The temperature range for growth was 25-50 degrees C, with fastest growth at 37 degrees C. The pH ranges for growth and methane production were 6.5-8.0 for strain 8-2T and 6.8-8.6 for strain 4-1, with the fastest growth at pH 7.2 for strain 8-2T and pH 7.5-7.7 for strain 4-1. The G+C content of genomic DNA for strain 8-2T was 38.9 mol%. The similarity levels of the 16S rRNA sequence of strain 8-2T with other species of the genus Methanobacterium ranged from 93.8 to 96.0 %. Based on the phylogenetic analysis and phenotypic characteristics, the novel species Methanobacterium beijingense sp. nov. is proposed, with the type strain 8-2T (=DSM 15999T=CGMCC 1.5011T).