From 85 samples taken during cruise 45B of the R/V SONNE within the Sunda Arc subduction zone and from solfatara fields in Java, thermophilic and hyperthermophilic archae- and eubacteria were isolated. The archaebacteria belong to the genera Methanobacterium, Methanolobus, Methanosarcina, Acidianus, Thermoproteus, Desulfurococcus, Thermoplasma and to two up to now unknown genera of hyperthermophilic marine heterotrophs and continental metal mobilizers. The eubacterial hyperthermophilic isolates are a new species of Thermotoga and a novel strictly anaerobe, thriving by H2/N03"-autotrophy.