Lowest hydrates of uranyl p-toluenesulphonate (UPTS) and anhydrous salt were synthesised. The dehydration-hydration processes were studied by thermal gravimetric analysis. It has been established that the hydrate shell of UPTS has a layered structure. The IR spectra of UPTS and its hydrates were recorded. It was found that the IR spectra of UPTS crystal hydrates of the same composition, produced in dehydration-hydration, noticeably differ in the range of water vibrations and are the same in the range corresponding to vibrations of sulphonate groups.