Compositionally similar samples of hydrated Na-X zeolite with 220-265 water molecules per unit cell are shown by X-ray diffraction methods to exhibit structural differences. Three samples, independently treated to maximize Na and H20 content, crystallographically resemble the samples studied by Broussard and Shoemaker, and Smolin et al. (space group Fd3m) rather than that of Olson (Fd3). Intensity data were resolved into component hkl contributions by treating the known framework sites as conventional heavy atoms. Difference Fourier and least-squares methods were used to reveal and refine the interstitial Na and H20 sites. The resolving and refinement steps were repeated cyclically until a self-consistent structure for each sample was obtained. All samples show differences in the detail of their nonframework structures. Fuller H20 loading leads to a higher occupancy of H20 sites generally and a lower Na occupancy of site II than in single-crystal samples. The occupancies of the sites in the 12-ring regions of all the samples have been interpreted in terms of two centrosymmetrically related Na(H20)2 units per 12-ring. The disorder is such that in some 12-rings the Na(H20) 2 units are linked mainly to framework atom O1, whereas in other 12-rings O4-networks are found. The crystallographic data agree with analytical data if 20 mobile Na+(H20)6 ions per cell are assumed to occupy the supercages of the powder samples, but only !4 are present in the less-hydrated single-crystal samples.