The surface tensions sigma of aqueous solutions of isobutanol, isobutylamine, and L-valine were measured in the temperature range between 278 and 308 K using the Wilhelmy plate method. The surface entropies, enthalpies, densities, and compositions were calculated. The results were interpreted in terms of specific interactions of the hydrophobic parts of the molecules adsorbed at the interface. Increasing surface concentration of two former solutes molecules causes, in both cases, a rearrangement at the surface, similar to that observed earlier for water+tert-butanol. The same concerns L-valine, although it was found to be a very weak surfactant, which can be understood if assuming strong interactions of this solute with the bulk water structure and competition between hydrophilic and hydrophobic hydration of its molecules. (C) 2001 American Institute of Physics.