We have examined proton exchange and thermolysis reactions for the phases A2TinO2n+1(n=3, A=Na; n=5, A=Cs. Thermogravimetric analysis indicated that dehydration of acid-exchanged materials occurs in several distinct steps, and X-ray diffraction and Raman spectroscopy demonstrated that structural rearrangement accompanies each weight loss. The final products obtained at approximately 350°C were isostructural with the new form of TiO2, TiO2(B). In the present work we investigate the structures of the acid-exchanged materials H2Ti3O7and H2Ti5O11·3H2O, examine the structure of phases formed during dehydration of these compounds, and discuss the relationship between the initial titanate structures and TiO2(B) formation.