Four kaolinite/CsCl intercalation complexes were prepared by different methods and characterized using X-ray diffraction, photoacoustic and diffuse reflectance infrared spectroscopy, and simultaneous DTA-TG. Sample A was obtained by wet grinding a mixture consisting of equal amounts of CsCl and kaolinite : in this complex the kaolin-like layers were not arranged in any preferred orientation. This sample contained a great amount of intercalated water which could be eliminated below 250-degrees-C. Sample B was derived from sample A by heating it at 250-degrees-C. In sample B, the kaolin-like layers were parallel with a c-spacing of 1.065 nm. Samples C and D were obtained by ageing sample A or untreated kaolinite, respectively, in a concentrated CsCl solution. Both of the latter samples were similar to sample B.