The investigation of the osmotic behaviour of representative salt types at temperatures above 100° has been extended to 150 and 165°. Experimental data are now presented on LiCl, KCl, CsCl, BaCl2, Na2SO4, and MgSO4, referred to NaCl as the standard. The possible significance of these results in the interpretation of the osmotic behaviour of aqueous salt solutions at these elevated temperatures is discussed.