The noble gases, krypton and xenon, were adsorbed on three kinds of molecular-sieves (AW-500, 5A and 13X), as well as on activated charcoals (Tsurumi-HC-30, Takeda-G, -L), at pressures from 10-2mmHg to 1 atm at temperatures ranging from —78—, 0— to 25°C. The adsorption isotherms of krypton and xenon on MS-5A and −13X are linearly proportional to pressure, and are considered to follow de Boer type isotherms. However, the isotherms for other adsorbents are shown to follow the Langmuir pattern. All the isotherms are discussed in terms of functions of the heat of adsorption and surface area. The adsorbents, that show the Langmuir isotherm pattern, are considered to be efficient for practical use in removing or recovering noble gases.