Abstract The effects of the degree of exchange and the dehydration upon the structural stability of silver-exchanged forms of the synthetic zeolite Linde 4A have been investigated by means of DTA, X-ray diffraction, and adsorption studies. The relative intensity of the X-ray powder diffraction decreased with an increase in the extent of Ag+-exchange, though it indicated no accurate information on the crystallinity. An exotherm on the DTA curves which shifted to a lower temperature with the degree of exchange became an indication of the collapse of the structure; this was in good agreement with the specific surface area of the sample heated at a higher temperature. From these results, the silver-exchanged zeolite A was concluded to be thermally unstable and to lose its crystal structure at a lower temperature than the original sodium form. It is also proposed that the comparison of the X-ray powder diffraction intensity is not suitable as a method for judging the crystallinity of zeolites A.