We present calculated potential of mean force surfaces for rotation about phi, psi dihedral angles of the alpha(1<-->1)alpha-glycosidic linkage in the disaccharide trehalose (alpha-D-Glc-(1<-->1)-alpha-D-Glc) in both vacuum and aqueous solution. The effects of aqueous solvation upon the alpha(1<-->1)alpha-glycosidic linkage are investigated through comparison of the vacuum and aqueous solution free-energy surfaces. These surfaces reveal that trehalose is restricted to a single minimum-energy conformation in both vacuum and solution. The exceptional rigidity of this disaccharide in solution may provide a molecular rationale for the antidesiccant properties of trehalose glasses.