Populations of the four major trophic groups of methanogens were enumerated by most probable numbers (MPN) on selective media in a sample of 13 soils representative of major types of rice soils. Dominant strains were isolated and their phenotypic and phylogenetic characteristics were studied. MPN counts ranged from 102 to 106 g−1 d.w. on H2, from <10 to 104 g−1 d.w. on acetate, from <10 to 105 on methanol, and from 50 to 106 on formate. In most soils, counts of hydrogenotrophs were higher than counts of acetotrophs, partly because acetotrophs were aggregated sarcinae difficult to separate into individual cells. Methylotrophs other than acetotrophic sarcinae were not recorded. In most soils, rods enumerated on formate were 5–400 times less abundant than those enumerated on H2, indicating that hydrogenotrophic‐non‐formatotrophic rods are probably dominant in ricefields. Dominant strains isolated comprised: 15 hydrogenotrophic‐non‐formatotrophic rods affiliated to Methanobacterium bryantii; three hydrogenotrophic‐formatotrophic rods affiliated to Mb. formicicum; one hydrogenotrophic‐formatotrophic rod not affiliated to a sequenced species; two sarcinae affiliated to Methanosarcina barkeri and Methanosarcina mazei; and one irregular coccus affiliated to Methanoculleus marisnigri– a species so far isolated from marine sediments only. Results from classical counts of methanogens and strains isolated from ricefields suggest the dominance of Methanobacterium spp. (mostly responsible for CH4 production from H2/CO2) and Methanosarcina spp. (mostly responsible for CH4 production from acetate) among culturable organisms. Both genera are probably ubiquitous. In particular, Mb. bryantii was isolated from 12 of the 13 soils.