Changes in the surface tension and in the surface potential of dimethylsulfoxide and ethylene glycol upon adsorption of chloroform, trichloroethanol and tetrahydrofuran (THF) have been measured. Surface excesses have been determined by fitting the surface pressure curves with a Frumkin equation. The derived adsorption parameters have been scrutinised and discussed. Adsorption potential shifts have been extrapolated to surface saturation conditions and analyzed in terms of surface orientation of the adsorbate. THF has been found to adsorb with opposite orientations at the surface of the two solvents. An explanation is offered. (C) 2003 Elsevier Science B.V. All rights reserved.