Abstract: Kamchatka is one of the most active regions of volcanism in the world because it is located in the transitional zone where the Eurasian plate，North American plate and Pacific plates meet．As a result，Kamchatka has numerous hydrothermal systems，which constantly release geothermal gases anti fluids out 10 the earth surface．Geothermal gases such as N2 and CO2 may prevail in the outflows but H2，CH4 and H2S occur frequently． Hot spring waters in Kamchatka may have multiple origins including meteoric and magmatic water．The temperature of these hot springs ranges from ～20 ℃ to greater than 90℃．Water chemisitry also varies dramatically with pH ranging from 3.1 to 9.8．Hydrothermal fluids are sodium chloride water dominant and may contain various dissolved constituents including K+ ，H3BO3，H4SiO4， Ca2+，and S042- ．Volcanic ore—formation prevails in the high thermal activity regions in Kamchatka and precipitates may be dominated by silica crusts，sulfur anti Hg—Sb—As—FeS deposits．Oils are also generated in the region and dominated by n-alkanes．More than 24 novel thermophilic microorganisms have been isolated from hot springs in Kamchatka．Most of these isolates are heterotrophs；however，autotrophs may be equally abundant depending on the spring conditions．Collectively，these organisms may play important roles in biogeochemical cycling of carbon，sulfur and iron in the hydrotherm al system．Culture-independent approaches and quantitative methods are now employed to enhance our understanding of the ecology and biogeochemical functions of microorganisms in Kamchatka hot springs．