The isothermal adsorption and desorption of organic vapors on a single soil particle was studied with the aid of the electrodynamic thermogravimetric analyzer (EDTGA). Toluene and carbon tetrachloride were tested at room temperature during their adsorption on Spherocarb, montmorillonite, and Carbopack particles. The maximum amount of either organic compound adsorbed was comparable to that required for one monolayer coverage of the particle surface area. Significant differences among various pairs of solid-organic vapor examined were identified and correlated to differences in solid pore structure and chemical affinity between the organic compound and the solid.