Kaolinite hydroxyl surfaces have been modified upon intercalation with cesium acetate under a range of conditions. Upon intercalation of both low- and high-defect kaolinites with cesium acetate at 25 degrees C, additional infrared hydroxyl stretching bands are observed at 3606 and at 3603 cm(-1). New infrared hydroxyl deformation modes were observed at 898 and 910 cm(-1) upon intercalation with cesium acetate. These changes are attributed to the hydrogen bonding of the acetate ion to the inner surface hydroxyls. The intercalation process involves the incorporation of water into the interlayer structure. When treatment of the kaolinites is carried out under hydrothermal conditions, intercalation is incomplete. The 001 d spacing showed strong asymmetry on the low angle side indicative of some expansion of the kaolinite layers. Changes in both the hydroxyl stretching and deformation regions indicate that water is being incorporated into the kaolinite structure at the elevated temperatures of 120 and 220 degrees C. Raman spectra of the 25 degrees C cesium acetate intercalated kaolinites show additional bands at 3606 and 3598 cm(-1). These bands are attributed to the inner surface hydroxyls hydrogen bonded to the acetate ions. The Raman spectra also suggest that some structural rearrangements of the kaolinite layers are occurring with consequential alteration in the defect structures.