Amino acids, necessary to form life body, are present in greater abundances in natural seafloor hydrothermal fluids over 200℃ than in ambient seawater, although these are unstable and decomposed rapidly under simulated hydrothermal conditions. Serine and aspartic acid, which are thermally labile amino acids, are detected in the high temperature fluids. Inorganic matters such as metal ions and minerals could protect these labile amino acids in the fluids. Most of the dissolved amino acids are combined form and L form, suggesting that these are derived from organisms around hydrothermal vents. In addition, low levels of non-protein amino acids content indicate that amino acids are fresh and not experienced thermal alteration for long time. Amino acids are important as common sources of carbon and nitrogen for heterotrophic marine microbes. The release of biogenic amino acids along circulation paths of hydrothermal fluids could be effective for the development of hydrothermal vent fauna. In this paper, I review the origins and characteristics of dissolved amino acids in the natural hydrothermal fluids and implicates importance of the biogeochemical cycle of nitrogen and carbon around hydrothermal venting in detail.