In this study the thermodynamic properties of various Oxo-alcohol ethoxylates related to their adsorption at the air/water interface and to their micellization have been studied. The effect of various additives, including electrolytes, alcohols, polar aromatic solutes, and ionic and nonionic surfactants on the cloud point of aqueous solutions of the same surfactants has also been investigated. Salting-out electrolytes lower the cloud point while salting-in species raise it. Except for the totally water-miscible alcohols, most hydroxylated compounds lower the cloud point. Phenols, aromatic alcohols, and amines seem to interact preferentially with the ethylene oxide groups of the micelles, leading to strong dehydration, and consequently lowering the cloud point. On the contrary, by forming mixed micelles, an anionic surfactant strongly raises the cloud point of the nonionic.