Structural studies of intrinsically disordered proteins (IDPs) entail unique experimental challenges due in part to the lack of well-defined three-dimensional structures exhibited by this class of proteins. Although IDPs can be studied in their native disordered conformations using a variety of ensemble and single-molecule biophysical techniques, one particularly informative experimental strategy is to probe protein disordered states as part of folding-unfolding transitions. In this chapter, we describe solution methods for probing conformational properties of IDPs (and unfolded proteins, in general), including the use of naturally occurring osmolytes to force protein folding, the quantification of coupled folding and ligand binding of IDPs, and the structural interrogation of solvent- and/or binding-induced folded conformations by thermal perturbations.