CHAPS, a surface-active derivative of the steroids' basic structure of the cholic acid {3-[(3-cholamidopropyl)dimethyl-ammonio]-1-propanesulfonate} has become a very important material in biological and pharmaceutical application. Investigations of the adsorption properties of aqueous, surface-chemically pure CHAPS solutions at the air/water interface were performed using surface tension and surface potential measurements. Unlike ordinary extended-chain surfactants, the amphiphilic structure of CHAPS is prone to adopt different concentration-dependent surface states of the adsorption layer. These are well reflected in the adsorption isotherm and in the electric surface properties. They are explained by changes in the adsorbate molecule's orientation and/or conformation as a result of the latter's different surface area demand. The versatile favorable application properties of the CHAPS molecule are obviously due to its complicated molecular structure, which enables it to comply with rather different interfacial and colloidal challenges.