Experimental infinite dilution activity coefficients gamma(1)(infinity) for toluene in aqueous solutions of five protein stabilizers, glycerol, ethylene glycol, glucose, sucrose and trehalose, are reported. The data were measured over the temperature range 273 K to 323 K. The concentrations of these stabilizers were chosen to match as closely as possible those used in the biochemistry field. For glycerol, the data were measured at four concentrations (0.5 mol (.) dm(-3) to 5.0 mol (.) dm(-3)); at the highest glycerol concentration, gamma(1)(infinity) was also determined at T = 268 K. Ethylene glycol, glucose and sucrose were used at a single concentration (1.5 mol (.) dm(-3)), while trehalose was employed at 0.5 mol (.) dm(-3). As the concentration of glycerol increases, there is a significant decrease-of gamma(1)(infinity) values with respect to the. pure solvent water case, indicating that this modifier is able to solubilize more toluene than pure water. At all temperatures studied, the presence of ethylene glycol also decreases gamma(1)(infinity) values. On the other hand, glucose shows the opposite effect, i.e. it solubilizes less toluene than pure water. The other three modifiers (glycerol, sucrose and trehalose), are unable to solubilize more toluene than pure water at low temperatures, but as the temperature is increased they become solubilizing agents. The modifier concentrations and temperatures, where less of the non-polar toluene can be solubilized, are those often used to store proteins, to prevent them from denaturating. The solute in (water + modifier) y(1)(infinity) data were analyzed through a classical thermodynamic scheme employing solution and transfer (water to (water + modifier)) quantities. We compare the solubilization power of the protein denaturants urea and guanidine hydrochloride (J. Chem. Thermodynamics 2000, 32, 1683-1705) with that displayed by the protein stabilizers used here.