The ordering of interlayer water and interlayer carbonate in hydrotalcite ([Mg3Al(OH)(8)](+)[0.5,CO3-.mH(2)O](-)) has been studied by using static H-1 and C-13 NMR techniques. Spectra were taken of both powders and oriented material. The results indicate that interlayer water possesses rotational freedom around the C-2 molecular axis and that the molecular symmetry axes of both carbonate (C-3) and water (C-2) are oriented parallel to the crystallographic C axis of hydrotalcite. The ordering is caused by hydrogen bonding between the hydrogen atoms of the main layer and the oxygen atoms of the interlayer molecules.