A new obligate halophilic methane-producing bacterium has been isolated from the sediment of solar salt ponds. This isolate was unable to grow at or below 12% salt concentration and used H2/CO2 (80/20) as energy and carbon source. No growth or methanogenesis was observed with other reduced substrates. This is, to our knowledge, the first obligately halophilic methanogenic bacteria described. Since the phylogenetic nexus between methanogenic and halobacteria seem to be relatively close, the study of this organism could help to understand the relations between these two groups of archaebacteria.